Cryptography is the study of encryption. Cryptology is the study of both encryption and decryption/cryptanalysis. Is cryptanalysis out of scope here?
Cryptography is generally considered a synonym of cryptology nowadays. Cryptology would of course be the better name if you look at the etymology of the terms, although you could argue that "kryptos" also doesn't cover the contents, as "hidden" hardly seems to cover hashes and random number generation.
Language doesn't evolve using logical reasoning; it contains many words that just kind-a stuck. Many terms - if not most terms - have changed meaning during the lifetime of a language; we would not even be able to understand persons that spoke old English.