It would surely depend on the SSD and the firmware it's running. I don't think you can entirely count on it. Even if it were working perfectly, and your strategy was to power the SSD on periodicially to refresh the cells, how would you know when it had finished?

NVMe has read recovery levels (RRLs) and two different self-test modes (short and long) but what both of those modes do is entirely up to the manufacturer. So I'd think the only way to actually do this is to have host software do it, no? Or would even that not be enough? I mean, in theory the firmware could return anything to the host but... That feels too much like a conspiracy to me?

Do you know any firmware engineers?