Agamon
Adventurer
No rime or reason that I can tell; I've seen a few other monsters where the attack modifier isn't simply (stat + prof) like you'd expect. Black bear is an example I've noticed.
I think it's a case where they're building monsters to fit roles, rather than building out from formula.
Right. Same reason the Carrion Crawler is +8 with it's tentacles. It's a flavor thing. Ghouls prefer to attack with claws, the bite is more clumsy (it did used to be human, using the hands to attack is easier than the mouth), and the crawler has 8 tentacles flailing about in front of it.
Nice to see monsters aren't a picture and a formula.