You should post again on what you're going to change, because i (at least) read that advice both ways, and I want to make sure you're reading it the way that was intended.

If your database is open to 127.0.0.1/{8,24,32}, it is open only to the local host; that is the non-routable localhost address and it's not accessible to the internet.

If your database is open to 0.0.0.0/0, it is open to the internet and anyone can attempt login. This is bad. Presumably you also still need a password, but never assume. Always have defense in depth - at least two things need to go wrong/be wrong before you're compromised.