I think the amount earned in a fair comparison is wrong here.

the x10 ihg points is standard and the additional 50% plat bonus is standard for that tier as well. Earned through the card, but not required to use the the card to get.

so he should earn 15x ihg points for his stay, regardless of card.

the comparison then is:

csr: 825 ur points
ihg: 1375 ihg points