By the time you posted, Apple had already turned off Facetime Group Messaging so it was no longer possible for this to work. So why post it like it was a current problem? Oh yeah, because you and Corey dislike Apple.
As for those asking who uses Facetime? Those of us with Apple devices who don’t want our every word being uploaded to Google/Amazon for analysis to be used to better “sell” us. That’s not just oldsters but everyone with an iDevice including kids with hand me down iPhones & iPads.
Was it a serious bug? Yes.
Were a lot of people exposed? Potentially yes, but not in reality because Apple shut down Group Messaging when awareness of the issue started becoming public. Yes, IMO they should have taken Group Messaging offline ASAP but we do not know the timeline of when Apple became aware of the issue. Did it take minutes for them to determine that disabling Group Messaging would squash the bug? Hours?
Will Group Messaging be back soon? Yes, Apple will be publishing updates that willdefinitively squash the bug in Facetime clients at which point Facetime Group Messaging will be turned back on (presumably only for those with updated clients.