I am surprised no one is refuting this, because this is such a widely used talking point for the anti-UHC crowd!
There's nothing to refute, really.
We have always had mechanisms of rationing in HC. The market has its means of limiting HC delievered, and if we chang the method of payment, that system will also have some system of rationing HC, too.
Failure to have some kind of mechanisms in place to limit HC delivered would be diasterous.
To some extent we're in such trouble now precisely because we don't limit HC enough right now.