I guess that is technically true, but if anyone who is NOT a VC is buying into the idea that VC backing is the only valid definition of a startup... you have drunk too much of the kool-aid.
I would say they more just look at it as an easy filter. While there will be some false negatives, you have very few to none false positives i.e., venture-backed companies that turn out to be non-startups but don't close or exit.
The example that comes to mind that breaks this is the failing startup turned dev shop in attempt to revive the startup pattern.
It's not the "startup" label that's a problem, it's that VCs breed a monoculture. There are lots of startups that don't secure funding because they don't fit the VC mindset. This is a survey of "what VCs want in their portfolios", not "what entrepreneurs choose to do", which are very different things.
