I can unfortunately understand why Valve would tip off Nintendo, to avoid being directly liable because it’s not the standard DMCA provision.

But, at this point, emulation, where you legally have the game and console, shouldn’t be illegal and they shouldn’t be preventing it.

As for the decryption keys, rock and hard place. Either that needs to not be illegal, or it’s impossible to emulate a game legally. Since emulation isn’t illegal, the former shouldn’t be either.