"It was decided 10 or 15 years ago that having a Guest logon to a Workgroup posed a major problem if the Security tab were to remain available by default."
Actually, I think it was more to do with making XP more friendly to people coming from the Win 9x line by trying to hide some of the complexity of NT Security. That's one of the reasons the security tab was hidden, because it was deemed to complicated for Home users to grasp.
At a guess, I'd say ForceGuest=1 turns on 'XP Home' mode, hiding the security tab and treating all network users as the 'Guest' account for sharing purposes. Still, it's only a binary switch so it's not exactly major hassle to try it and see.
Since the whole thing has effectively been superseeded by HomeGroups as a much easier way of configuring sharing between Home computers, it seems a bit late to complain about the KB article now.