I find this to be a slightly weird argument. Med school degrees do have varying levels of quality. Moreover, in the US, you cannot be licensed without residency -- residency is practicing under supervision, essentially a skills-based set of active tests. Then after the residency program many physicians go for board certification, which is additional study and tests (run by a professional cabal that makes a ton of money off of questions about beaver fever, for instance).

Well, anyhow, you already do require skills-based assessment if you are seeing licensed physicians in the US. They don't let ppl practice with only book learning.