Lumber liquidaters sales rep says 5/16 inch bellawood solid hardwood floor is too thin. Is he right?

He sounds like he knows what he is talking about. If you go with a real thin wood then you will not have enough if you ever need to resurface. If u do drop something on it like a beer bottle and it breaks it can gash the wood and en up showing the underlying material. It does seem like a really large investment, but u will end up kicking ur self in the long run if u go with the thin wood.