They are, however, secret codes, and should be regarded as confidential. Just because you can divulge them without direct harm does not mean you should publish them on billboards and Facebook for safekeeping.
This is true but isn't relevant to my advice. If you can't see the difference between keeping a nondescript piece of paper at the bottom of a drawer at your parents' house and posting it on Facebook then you should not be making any decisions relevant to security. And using the word "secret" causes people to treat the codes as more precious than they really are, and make bad decisions like not printing them at all.
1. System reports "print out these recovery codes and deposit them in multiple places so you will never lose access to your account". User John Doe posts his security codes on his Facebook page and gets hacked.
2. System reports "print out these security codes and store them in a safe place". User prints them out and stores them in a drawer, but his house burns down and the user loses access forever.
Both scenarios are shitty, but I think 1 is more likely.
Of course, you could write a detailed guideline on where to store your codes, and that you should share them with some trusted people but not everyone etc. But who's gonna read that?
People who understand security already take threat models into account, but those who don't need very simple guidelines.
