That’s exactly how it works – the incoming email forwarded from the SMTP account goes to the group, and when email notifications are sent from that group inbox, they are sent via the same SMTP account. This does not handle full syncing like IMAP (e.g. labels, archiving/unarchiving, deleting) but it probably gets you halfway there. The caveat with both IMAP and SMTP support is that they are both limited to the group inbox.