It really does seem that getting too deep into niche shipping fandom absolutely kills some people's media literacy. Like, I was reading this interesting anon post on Nancy's blog [X] about following a rewatcher going on about bi lighting and expecting a romantic HEA from fucking Supernatural and it sent my brain off on a tangent.
I mean, I remember thinking literary interpretation in school was so fucking absurd when it got to the point of analyzing a goddamn autobiography and waffling on about the author remembering the grass in the spring being green when they moved as a symbol of rebirth. As absurd as I still think interpreting on that level is? It did work thematically, because the interpretation matches the surface level of the story - that was when the character's life started through a period of growth/rebirth. Did they intentionally mention the grass for the symbolism of the color green, consciously or unconsciously? Fuck if I know (or care, tbh).
The problem with the way hellers (and other similar conspiracy shippers) try to use this kind of interpretation is that they ignore several majorly important factors that apply when you're talking about an open canon rather than a closed one where you know the ending. When you do this with a story that's finished, where you know the whole picture? Even if you're so openminded about what the story could have been despite all genre conventions and other outside information that your brain is on the verge of falling out and rolling away down a hill? You can filter out the noise of potential symbols and meanings that do not match that finished, overarching story. And there is a lot of fucking noise, because our brains really, really like to find patterns whether they exist or not - but most random details are not intentional symbolism, and most symbols do not have one single definitive meaning. With any sufficiently large text (which SPN definitely is), you could pick out enough random symbols and meanings to point to literally any-fucking-thing you wanted as a possibility - but without knowing the end that's no more an indication of what direction the story is actually heading than any other randomly chosen set of symbols and meanings.
In the above example, let's say you don't know anything about autobiographies in general, that author's life in particular, and stopped reading at that chapter to try and predict what'll happen next. Aha, the grass out of the window when they moved in spring was GREEN! Well, yes, that might symbolize growth and the character's life finally starting on a new positive path now. But green can also symbolize naivety and/or hope, and that could have been a brief shining moment of good possibilities before things went even more to shit. Hell, it can also mean jealousy, where maybe it would turn out their best friend who stayed behind got an opportunity they missed because they moved. Not only are those not the only possible symbolic meanings of the color? The author might have also just decided to describe the grass out the window as green because grass is generally fucking green in spring, yo. A major part of the reason someone can sit and pontificate about the ~*deep symbolic meaning*~ of that passage without potentially being obviously hilariously wrong is that they DO know where it ultimately leads and have tossed out the interpretations that explicitly don't fit the story.
What the shippers in question try to do is insist they know what the ending HAS TO BE ... because reasons. As such, every single symbol they find which could potentially signal that ending must be doing so, despite any number of other possible meanings ... because reasons. Naturally the symbols that they find are actually meaningful symbols as opposed to every single other random detail in the story with potential meaning ... because reasons. Then we reach the end of the story and they're oh-so-shocked that because reasons ... isn't a real basis for anything, actually. HOW COULD MY AMAZING INTERPRETATIONS HAVE BEEN SO WRONG WHEN I CHERRY-PICKED THEM SO CAREFULLY? CONSPIRACY! HATE CRIME! WAAAAHHHHHHHHHHHHH!!! There was never any basis for their assumption they knew those symbols were legitimately symbols with significance, let alone their assumption they knew the ending - other than their own fixation and entitlement.
Just to finally drive the point home about how absurd it all is? In my original autobiography example, we're talking about an autobiography of a famously successful person. Any remotely savvy reader can make pretty reasonable guesses from the genre conventions of autobiographies, that person being Known Name successful, and context in the surrounding text about how important that move was going to be to the author's life to be such a focus - and therefore what things in the surrounding text might be *cough* reasonable symbolic signposts. There's still some potential to be wrong about the particulars of that moment, but it's a more educated guess about where the story is likely to go because of everything you know about the protagonist and the genre.
Similarly, any remotely savvy watcher who has some familiarity with horror fantasy as a genre, who spent fifteen seasons watching a show where everyone fucking dies and two brothers are obsessively and intensely brothering each other to the exclusion of all their other relationships every episode, from every single premiere through every single finale? Nevermind anyone who also basically ever heard the showrunners and stars talk about it? Is not going to reasonably think, oh, hey, this is totally going to end with the single central relationship of the show indifferently separating to turn into a fluffy HEA romcom with random side characters. Even if you take off the ending of that sentence which is "because I totally found a bunch of secret clues in food and lighting that told me so".
It makes no fucking sense on a micro interpretation level of symbolism and signposts, and it makes no fucking sense on a macro interpretation level of genre and overarching themes. But, like, they really wanted it, so who cares about that? Um, all the rest of us who actually liked the show for what it was, not an entirely different thing we tried to convince ourselves it would eventually have to be ... because reasons. Especially anyone who gives even half a shit about how decent storytelling in media actually works.