“This is Depp’s usual way of speaking.”
He didn’t speak that way in “Jump Street”, IIRC. When have you heard him speaking not in front of some camera, or not out in public? It’s his public persona and he works at it.
I caught about 15 seconds of his testimony ... ACT-ing.
He’s on youtube in some interviews over the years.
Jump street was a show, that’s acting.