This simple answer is satisfying to many who otherwise prefer single-payer plans, but doesn't really hold up to scrutiny
I mean, it fails the even more basic scrutiny that Canada simply does not have a single payer for pharmaceuticals, or even a handful of single payer provinces. It's much like the US in structure (out of pocket or private insurance), simply with price controls.
If country X (with single payer plans) does the same thing, the only choice the pharmaceutical company has is to not be covered by insurance, which mean they won't sell their drug. Also the state can just pass laws to make the pharmaceutical company life's miserable. UHC can't do that.