On Jackson Browne’s “Red Neck Friend” (probably my alltime favorite JB song), piano credits went to a “Rockaday Johnny”...later identified as Elton John.
Some some trivial information that popped into my head when I read your post.
As a musician I can understand how some may see other keyboard players having more aesthetically better music than ELP or The Nice. However, from a perspective of technical ability, no one came close to Emerson