That’s good to know as most travel agency bookings don’t allow you to earn hotel points (not just IHG it’s the same with other hotel schemes as well).

I’d note the qualifier about earning being on room only bookings whereas you appear to have a package even if the flight is free.

I’ve just remembered that if you have the IHG booking confirmation number from your Costco booking (or if not see if they can give it to you) you can connect it to your IHG account and once it does that it should show the estimated points you’d earn.