If you had 2.2.0 installed already, and your CSS is working fine, you don't need to "Rebuild All Styles". However, if you had an earlier version than 2.2.0 and you upgraded to 2.2.1 PL 1, you will need to enable your forum's debug mode in order to see this link. This is an unfortunate restriction that we did not realize and is probably why so many people have experienced problems initially getting their wiki CSS built. In the next build, this link should show all the time.
However, even if you had 2.2.0 installed, you will still need to "revert" all VaultWiki's templates. Your AdminCP's home page should alert you of this. If you don't see an alert, you don't need to revert anything.