It's less that high level users have specific needs and more that the workflow doesn't exist for high level users to worl efficiently. You see this a lot when you listen to what people actually do with GIMP. They either only use it for small, quick jobs or they'll start with GIMP and migrate to another software when it grows complex.

That said, GIMP is lacking in two particular feature areas, its selection tools and its completely non-existent nondestructive editing tools. The transform tools are also a lot less wieldy, and GIMP's text tools, on top of being unwieldy again, have rendering glitches in their antialiasing code that gives everything a green tint on my machines. There's many pain points like that where things are lacking, more difficult to use, or subtly broken. Fine if you don't dive deep, but increasingly frustrating if you do.