you are correct, they are not the same... the head:body ratio is much different. it's most obvious if you look at the shoulders, I think: primagi models have broader, slightly more realistic shoulders compared to the aipri ones which are barely wider than their ears, more like a little kid's proportions. aipri hands are also much larger, compared to both their arm length and their head size. I think that one should be pretty easy to spot too. there's more (shorter arms, legs, and torsos; less defined waist) but that's maybe less easy to notice? it really depends on the coord.
there are very similar face types, but they have differences too. it's hard to tell from the stock images, but
aipri eyes are bigger proportionally to their face, and the main lash line or whatever is comparatively HUGE so their eyes really eat up their face (sorry, I don't love this haha). their noses are even somehow less visible!