I read this carefully too when booking a rewards room for relative who was 18. Only to have the hotel turn the party away because their check in age is 21. It was late and they said too bad, our policy is 21. But I wasn't given any notification of this on the IHG confirmation that I received. It was a complete surprise. We had to scramble to find them a replacement at that late hour. IHG refunded the points but the hotel charged a "no show" fee when they knew we showed up but turned us away.