Thomas Shey
Legend
In D&D 5e, you don't actually need the skill but it obviously helps increase the chances of success.
You technically don't in PF2e either, but its unlikely to work except at the lowest levels, i.e. you're only likely to know things about low level monsters in practice, and then only if you have a decent INT and/or roll well.
Telegraphing mitigates the chances something is seen as a gotcha, be it new monsters, traps, or anything else where someone might feel their lack of knowledge (or inability to act) was used against them.
That's fair, to a point, but then most metagamers will assume the fix is on and won't try it in the first place. The ones that do, though, probably won't take it in good humor.