Hmm, what I mean is, I open up Steam on my Linux system. Usually it remembered my login but sometimes I need to login again. If I then type my password, it says: "type the code we emailed to continue".

So if I wouldn't have access to that email account, I couldn't login and lose the Steam account, even when knowing the password.

Although, some of the methods from the link would still work, so that's solved, I guess.