Sorry if this becomes a double post guys. I am new here and to Pathfinder (never really played 1e but so far love 2e). I have a question about adding a skill at high levels. Unless I am mistaken, a 20 level character could, say, become trained in acrobatics, and by adding proficiency (which adds level in the mix), that character is now suddenly better at acrobatics than a level 6 rogue who may have done acrobatics his/her whole life? That seems crazy to me. Please correct me if I am missing something because this is driving me nuts.
Yes, you are technically correct.
Note that skill bump is worth a bit more than others because the high-level PC would typically be giving up an opportunity to gain a Legendary rank in a Master skill. And using a high-level class feat to pick up a Dedication (and perhaps getting a skill that way) would be a poor choice.
Also, I'm of the opinion that every high-level person should have taken Untrained Improvisation by then anyway.
Non-mechanically, we are talking about a superhero. Whether it's an afternoon training montage, a blessing from a goddess (hidden or overt), or tuning themselves in with reality's weave better, they operate on superhuman levels where yes, they will be better casually at a task than normal people who have dedicated their life to mastering that task.
ETA: Unlike most RPGs, there isn't only one measure for skill expertise. There's the raw number rolled and the rank of proficiency. Each means a different thing even though they obviously interact. It's nuanced, perhaps too much though I like what it's trying to do.
I agree in short with Castilliano, without building characters from level 1 and moving up and finding Untrained Improvisation that could be confusing. As he never played P1 and is starting with P2, The number of skills is vast to say the least.
Also you would not want to give up the chance for reaching a legendary ranking proficiency.
It still allows for an old dog to learn a new trick or skill in this case... and still have an opportunity to fail at it. After all just because you just learned it does not mean your the best at it. That's where the proficiency plays its part in the question above.