I have several entries where the URL is different but the password is the same. Changing one password changes it for all sites. This works when I use KeePass itself to populate username and password. It does not work with the Kee browser plugin.
I wouldn’t recommend using it if you can avoid it - especially when the most common use case for this in KeePass is already covered by the ability to assign multiple URLs to a single entry. Although it can be useful at least as a temporary measure when a complex field reference setup is already in use in your database.