I don't think I understand the point you're trying to make. 400 acres in Greenbrier and service in the county militia does not suggest aristocracy. If the name "McCoy" itself weren't proof enough, the fact that they were here at all very strongly suggests that they were as common as everyone else.
What often happens, however, is that genealogical researchers will find one source that reads, "Mary McCoy", for instance, and another that reads, "Elizabeth McCoy", and then mistakenly assume that it was the same woman with two names. If indeed this woman was born before the Revolution, she is almost certainly either a Mary or an Elizabeth, but not both.