a) who cares who coined it, it is a classification used by many and quickly conveys the shared concept that matches that classification, which is the overall point of language
b) Coinbase is many products. Coinbase Staking is the one that matches what was described above. Don't conflate the front facing CEX for everything they offer. No different than Amazon not being a bookstore, nor just an ecommerce platform. It is many products. The context was solidified amongst several other products with similar offerings. Coinbase's various CEX products have nothing to do with their Staking product (or the Lending one they were going to try, of Vault or several others)