If this really is a true group booking, then I think this sums the situation up perfectly.

The organiser may well have arranged 'block-seating', could possibly have upgraded everyone; all sorts.

Group bookings almost always require desk check-in too, despite some marketing messages.

The only thing that puzzles me slightly is that COmitted reports various different error messages in MMB. A vanilla group booking wouldn't even recognise the PNR in MMB, let alone throw up booking or passenger-specific messages. G Class is used for groups, but also for various other types of booking including staff (Hotline) and connecting travel.

I'd be interested to hear how this all pans-out, but as it stands, it looks to me like the OP will be travelling as the organiser plans.