As others have mentioned, it's really just a mess. There are few things more "never-staying-here-again" for me than "we have upgraded you to the club floor, but you can't use the lounge".

FWIW, I can't recall a complimentary CP lounge upgrade where I thought to myself "I might actually pay for this". So that already puts IHG behind Hyatt, Marriott and Hilton for me.

ICs would be a different matter, yet of course nobody really expects an upgrade to lounge access there...