If you are talking about here
WORKGROUP is only the default. You can name it anything you want.
It's handy though if all your computers have the same "workgroup" name as it lends itself to better NetBIOS interaction on the network.
Not as critical as it once may have been, but generally still a good idea.
AND
It doesn't impact "home group" which is basically a Windows construct that helps sharing among other home group computers but personally I never use it.
I just use a work group name (same for all my computers) and share the old fashion way.