I've shared your worries regarding stitch with my Polarn (also amazon) who's beak seemed to grow out of control even if he was constantly chewing stuffs. So I started encouraging more chewing of wood and more chewing rather than breaking. Meaning he always breaks off corners and edges of stuff. But I decided to get 2"-3" thick natural branches (sometimes even thicker) then took the power drill and drilled holes and jammed nuts and seeds into the holes to really encourage him to work through the wood to get them treats. This does come with a slight downside though. Rather than debarking his branches he chews em straight off from time to time. But then I got plenty of trees and it can't be bad for him couse his over growing beaks seems to be under control ATM.
But I shared your thought of "an amazon needing it's beak trimmed? Huh?" when I first noticed it.