Ah ok I see your point. I assumed single payer meant "nobody pays out of pocket for anything" but you're right that 'anything' is really "what is covered" and that can theoretically be defined in arbitrarily complex ways. Apologies for the misread.
All the people against socialized medicine are more likely to be unvaccinated and thus would get pissed about this disparity. They'd demand to be treated equally to people without preexisting "conditions" (of not liking vaccines)
+ 1000. Frankly it would not seem so pie-in-the-sky to mail all these tests if they had the same costs as they do in Europe (5-10X cheaper!) AND it would be less necessary bc people could afford them better on their own.