I don't think it's fair to the candidate to expect them to think that when a recruiter says "suit up" they mean in t-shirt and jeans or cutoffs.
But you do highlight the flaw of natural language, where it only works where there already is a shared understanding. When quite often there isn't. Heck, 90% of the comments on HN are from actors having different understandings for technical jargon and talking past each other because they aren't even talking about the same thing. Such is the tragedy of the human existence.