Yes, you can. macOS ships with the account disabled by default, but you can re-enable it if you wish. Most of the time there is no reason to do so.

> If it was previously possible to create a root account then I guess there's no way to tell the difference between those who created the password as a response to the vulnerability and those that knowingly created a root account.

Yes, but this difference doesn't matter. By creating a root account you have made your computer less secure anyways, assuming that we didn't have the current issue at hand.