Poor clean spiders.

But I get what you are saying, it makes some intuitive sense.
In my case I think I've (as a kid) narrowed down the technical memetic part mostly to the very centre-point where the 8 lines end, so basically my brain recognising the legs (starting from the end of the legs) & then seeing how they "end" up in one narrow place (so, relatively to spider leg size, if the sternum looking from the bottom or the end part of prosoma from the top is "too tightly together" or even too perfectly round/octagonal shaped).
(And spiders differ very much in that regard, even the same one in relation to how well fed it is :D.)

Why? Idk, but doesn't feel learned.
(It's still there, but not the default/I have to think about it more actively.)

That I remember (again, as a kid) I was only triggered (differently than described above) by one "too smooth" species, the poor, harmless, misjudged beneficial, cute (well, as all spiders) wasp spiders.
I didn't harm them but it's a sad memory for me bcs the smol town (or the whole valley?) I grew up in basically doesn't have them anymore. Bcs we hate flowers/biodiversity, but love grass & pesticides I guess. I should be glad they were even still around for me to experience them.

(No pics bcs you mentioned you only like unshaven butts & legs.)

Kill it with ~~fire~~ water