The entire 300mm process is different on a microscopic level. For instance generally 200mm fabs don't need to use copper at all because the benefit of that is

The entire 300mm process is different on a microscopic level. For instance generally 200mm fabs don't need to use copper at all because the benefit of that is the dual-damascene process which isn't seen on the bigger tech nodes. Wafer stresses on 300mm wafers is dealt with a lot differently too so that is factored into the manufacturing processes as well. The major transition from 200mm -> 300mm will be when people like Broadcom use newer nodes for their chips as they go from iPhone 13->14->15->16...and eventually that will require 300mm processing.