In theory it should but this has not been my experience, (with the versiplug-R anyways). My ski has been upside down many times with only minimal water intrusion. Perhaps the most important detail is how well your ski is sealed in the first place? My hood seal is perfect and even though I still have the hood venting and dual breathers in the pole, I still don't take on much water when upside down.
I think it's a risk regardless of what you use, be it a scupper or versiplug and certain situations will make the result worse. I like the fact that the versiplugs are smaller and don't breath as much as a 2" scupper would so even if it is allowing air to escape, it's doing it at a much lesser rate.