I would say most players age 14+ are skating on 5/8” or flatter in North America. Those players also prefer profiles that are shorter.
In Europe, it's pretty standard to skate on a much flatter hollow and longer profile.
Tydan sells pro stock steel, you can see the different profiles, and it's always the European players that have a much longer profile and flatter hollow. Example, Nils Hoglander and Elias Pettersson skate on a 13/26 profile and likely a very shallow hollow. Willian Nylander skates in a 15' profile and likely a very shallow hollow.
https://tydanblades.com/collections/pro-stock-blades