The secret way to start the hidden multiplayer mode is part of the charm. I had fun explaining to my bros on Discord how to input the code when we were playing through netplay or Parsec and watching them be amazing that it had a 2 player mode this whole time that nobody really knew about. It's nice to have a hack that skips having to do it, but it was still pretty darn neat. The 2 player trick also works on the version of the game included on Switch through the SNES Classics app for Nintendo Online. So if you have friends on Switch you can play with, it works on that too
edit: also it's not a "secret code" like a password but is instead actually a button combination that has to be done using both controllers (which was what was charming about it)