Do you trust that the people who were working at Nintendo 30 years ago aren't trying to rob you? If so, you can (definitely even if you can't you definitely can) learn to generate your own seed phrase with dice or something using pen and paper. Then, with the Nintendo 64 handling the parts you don't know how to do, the only verification you need is seeing if anyone ever gets different results from the Nintendo 64. The only thing it could do is take the seed phrase and spit out a mismatched wallet address, pretending it matches, but the more people use it without anyone ever noticing it doing that, the more it can be trusted for that step of the process. If everyone for years always finds it takes a seed phrase and makes it into the same wallet address it would get from any other app, that's pretty good verification.