I was under the impression this was true feature-set wise. I may be wrong though and am happy to be corrected.
Almost. Go had the advantage of M:N threading with its goroutines and elegant CSP implementation.
Calling something a superset usually means it's actually an expansion of something... kind of like C++11 might be a superset of C++03 (not sure if that's accurate).
That's a really strange metric to use. It'll rarely be true, except in a sort of Turing completeness way.