Safer probably. I don't consider anything in this scene as "safe".
It would be trivial for Nintendo to check if you've bought the game or not when logging in. But they don't, but they could at any time.
Can they do this without forcing you to have a NNID to play online?
In theory, yes. If you have a connection to the internet, they could certainly pull some stats from your system, and blacklist it on their end. Or silently push something over to your system. Has this happened as of yet? No. But that's not to say it couldn't.
No software can be updated without your consent
Where on earth did you get that idea?No software can be updated without your consent
No software can be updated without your consent