If you're in a group it should be on you to add the group mint. That should be part of group onboarding. If you don't add that mint then I don't see that as any different to not adding a LN address here.

If you take the view that Nostr doesn't scale outside of a small world context then what happens in a big world context (i.e the current wilds of Nostr, even though to be honest here is still like a group in spirit) ins't indicative of much.