i'm inclined to believe that pro is aimed at people willing to drop a ton of money that think they're pro more than they actually do professional work, and that's sort of been a lot of apple's theme around their "pro" products regarding photography
It is just an upgrade to an existing lineup of Xs+Max, but with a reworked naming scheme (similar to iPad vs. iPad Pro). It is about as Pro as Xs+Max were.
Do you see a lot of artists using iPad Pro as their main tool? Me neither, but I do see a lot of them using it as their secondary tool that also doubles as a general-purpose personal computing device. Which is what, I feel, iPhone Pro lineup was made for.
