Do you expect me to believe that all the people, who, say, downloaded the leaked copy of Tears of the Kingdom, dutifully purchased a copy upon release date?
I wrote 'smacks of piracy’ for a reason. But I do not doubt for a moment that the main motivation behind current generation emulation is piracy, and that finding a person with a one to one game library real and emulated is a remarkable feat indeed. These systems and their associated games are neither hard to find, nor difficult to run, unlike older consoles, so there is no excuse if you wish to experience the games as they were intended.
Even if downloading it for the purpose of having a backup is your goal, it's still piracy in the UK and the US. There is no difference.
Fair use means you are allowed to make a copy of your OWN legally owned/purchased copy. But if the only copy is on a digital platform, then you aren't allowed to have a pirated copy as a backup measure.
You can disagree with me if you want to, but them's the legality of it.