Because you just run a script in poweshell and it gives you a legit licence. There have even been reported cases of Microsoft support advising to use the script when a customer has a licence issue.

Yeah for sure, I think the user had to provide keys in the latest Yuzu anyway?

It was donation builds with support for tears of the kingdom before released that screwed the project. The code itself was legal afaik.

My understanding is the prod keys are required to tell the software (e.g. games) that it is running on an authorised device and passes certain checks / DRM.

To run the software without prod keys would require (I think) patching each game individually to skip those checks. So it could be possible but wildly impractical unless some other work around is found.

Buy one get one free though - it’s actually 24 x 330ml for £15