Paired with allowing people who own the original to upgrade for $10 (and I’m assuming something similar in the UK) when they’re charging $50 for the remaster if you don’t have the original, that makes sense. They’re just closing a loophole.
I’d much rather they double the existing game’s price than for them to charge $25-$30 for the upgrade or to even just not have one outright.
It sucks for anyone who’d been planning to play the original and who just hadn’t bought it yet, but used prices for discs should still be low, so only the subset of those people who have disc-less machines are really impacted.
It doesn’t matter if it’s emulated legally or not. They can issue a takedown for showing gameplay captured from an NES hooked up to a CRT if they want.
A fair use defense has to be defended in court, and it’s not just about whether you’re right but also about whether you can afford to fight.
It’s also not certain that a fair use defense would fly. One of the elements for determining whether fair use is market impact, and I suspect that Nintendo’s lawyers would argue that demoing that their games can be emulated - even if the specific demoed games are not being sold - has a negative market impact, since it makes people who might buy a Switch and a Nintendo Online membership to play the official emulated games less likely to do so.