This is relatively minor in the grand scheme of things, but something I’ve always found annoying has been cleaned up. The monster version of Sneak Attack is no longer listed in the Ability Glossary, which means it no longer has hidden rules about what weapons it works with. Which means that kobold warriors can now sneak attack with their spears, like their stat block says!
This plus explicitly listing which creatures are immune to bleed damage shows that Paizo is cleaning up some of the “obscure rules hidden in places you wouldn’t think to look” problem what PF2e sometimes has.