Groups.io was founded by Mark Fletcher[0], who in '97 started the mailing list service that Yahoo! eventually bought and turned into their Groups product. They're about 10 years in and he posts weekly changelogs and updates[1]. Nonetheless, they're small and one might guess there's a high bus factor here. (Sorry Mark!)
I think it's a toss up either way. I hadn't seen talk of Google Groups being internally significant until this thread, but they've burned enough similar products that it was barely a consideration for me.
[0] https://en.wikipedia.org/wiki/Mark_Fletcher_(businessman)