I think you've got it backward. Any general member T&Cs will be overrules by the specific T&Cs of the certificate which say "Terms and Conditions ... This certificate is valid for accomodation only".
I also don't agree with your position that the hotel industry can simply re-define the usage of English words to their liking.
But I think we should agree that it is rather "cheap" of hotels to not honor the same terms on the free night as were honored on the paid night. Accepting this leads down a slippery slope to where the hotel says the room for the second night doesnt have to be the same room as the first night, because all the certificate says is "is valid for a complimentary room night". It doesn't say in what room.
HTB.
Not surprisingly,
HTB, I disagree. Whatever the certificate says the terms and conditions of membership are only set out in one place only -in the rules we all accepted, by implication, when we became members. If there is inconsistency, those terms would prevail.
I don't think that the hotel industry is defining the words by anything other than the practice in that industry. That is the context in which the words are interpreted.
Finally, I don't necessarily disagree with you that some aspects of the way IC hotels interpret the rules are "cheap". Sadly, as long as they are within the rules, that is their right and its our right to stay somewhere else.
As I said in another thread, the language of the various documents IHG relies on is very poor. There are inconsistencies and lack of clarity. They are in need of an overhaul. However, an overhaul may be to our disadvantage if it removes doubt and confirms the lowest common denominator.