Ok. That makes sense.
Here's something else, though: I sent an invitation to an email address that I know has never created a password. I clicked on "accept invitation" and was taken to the group's home page. So far, so good; at that point, the email address could have clicked on "log in," But it decided not to. As a result, the email address was IN NO WAY subscribed to the group, even by email.
It seems now that clicking on "accept invitation" requires creation of a password in order to even result in email subscription. It does not subscribe the member to the group; the member shows up as "sent" in the outstanding invitations panel, and does not show up as a member.
I think this needs to be clarified (or possibly it is still changing). As I understand it, at this point, from an invitation:
(1) replying to the invitation email subscribes the member to the group (as an email subscriber); but
(2) clicking on "accept invitation" does NOT subscribe the member to the group in any way, even just as an email subscriber. Instead, the invitee is taken to the group's page and MUST log in to be able to join (or subscribe). I think this is non-intuitive and should have an explanation in the invitation. I would think, as an invitee, that clicking on "accept invitation" does MORE than replying to the email, not less. Right?