'Cabana' is just the Spanish word for 'cabin'. Like 'cabin' it can refer to various types of structure, so there is no categorical answer to the question whether CCR cabanas are "really" cabanas. Clearly they are not thatched beach huts or pavilions where sea breezes gently waft through sail-cloth drapery. But yes they are a sort of cabana, I would say.

I suppose the operators call them cabanas rather than cabins for the same reason they call the Concorde Room a lounge rather than a waiting room.

They get a bad press on FT but I think they're a useful addition to the facilities. I like the privacy and the fuill-length couch for lying down/dozing. They work best for solo travellers or couples who are comfortable sharing an open plan bathroom. The style is more functional than luxurious but that's appropriate for a place where you'll spend a short time in transit.