I agree that both rooms should get credit. A similar situation occurred with me when I ws doing my Marriot gold challenge. My wife was going on a business trip and asked to apply my member number to the stay. They originally said no, but she said that was the only reason she was staying there and would go somewhere else and they relented. Actually they also upgraded her to a suite !!
If I stay at a Hyatt and bring family and need two rooms, I should get credit for any rooms I pay for , because I am the reason they are there