The way OP abstracted it makes it sound weird, but this is the normal, expected behavior.
Think about it: if you have a friend with photosensitive epilepsy or migraines, you generally warn them about flashing lights. Same goes for your friend in recovery with alcohol. Same goes for your friend with sensory processing issues with loudness. (In some of these cases it would happen as part of the planning process, not when you're about to walk through the door.)
"Bunch of us are going to Sammy's this weekend, do you want to come? Just so you know, people will be drinking."
This is not weird.
"It's going to be loud in here, you might want to put in your ear plugs"
This is not weird.
Content warnings are an accessibility feature. That most people already do in many daily situations. ("Just so you know, your ex is going to be there", "Do you want to watch this movie with me, Just so you know it gets kinda heavy")