While these polls aren't practical -- in that a Biden vs. Cuomo race will not be happening, certainly not in states that have already voted -- I think they are a very interesting measure of the level of dissatisfaction there is with Biden as a nominee. And you can't say it's just Bernie Bros, because Cuomo is ideologically aligned with Biden and pulling better numbers in OH and TX than Bernie ever did.
I think Cuomo is getting inflated support thanks to undeserved good press that would collapse were he to run a national campaign in a post-lockdown environment. Once it got out that he was trying to cut Medicare and being attacked from the left by Schumer of all people, there'd be a reassessment within media that's currently lauding praise on him.
In the UK, we're already beginning to see a reassessment of the competence of our own government's response. When the dust settles, I predict a lot of inflated favourability ratings are going to go down across the world.