Well, first of all, you didn't look in the right T&Cs: you looked up the T&Cs for Amabssador membership, which isn't a requirement to make reward reservations. Better look here:
http://www.ichotelsgroup.com/h/d/pc/...l#rewardnights Indeed, there is no limitation. To the contrary: it specifies that you can reserve more than one room.
Secondly, I don't think what you quote is meant for reward nights but for things like booking-guarantee and upgrades.
So, what did the hotel mean, and how did the story end? And how does the hotel check if the OP stays in the room with his mom or not?
HTB.
Well - not really - at best there are two sets of rules that appear contradictory. And the rules mean not what you say or think they mean unluckily - but what they actually state. Just choosing the set of rules you prefer doesn't negate the other set which was clearly the set the hotel were relying on! And the other rule on both sets which states that they can do what they like when they like overides both.
Good luck
evh5150 - let us know how it goes.