That's not what you said. You said the person checking in is the one who made the reservation. GUWonder is saying otherwise: if the T&C stipulates that the Diamond member must check in to receive benefits, that doesn't necessarily mean the checked-in guest has to be the one who made the reservation. IHG only says the member must check in to receive benefits. I'd like to disagree with GUWonder in that the T&C doesn't clearly state that only members who booked the rooms receive benefits. Perhaps IHG is implying it, but it would be nice if they explicitly mentioned it, like they do with group bookings: Diamond and guest receive full benefits if booked by another entity.