and while i am not a credit card T&C expert, i think when there has been a bait and switch, the credit card charges ought to be disputable.

big big thumbsdown to CX. had i been in OP's position on the flight, i would have been fuming, and if i had discovered the problem with the seat early enough, i would have exited the AC and demanded a working J seat before reboarding. let CX find another sucker to take the broken seat.