Signing is a subset of encryption, so it's not correct to say that no encryption is used in the protocol.
Is it not fair to say that signing is a subset of cryptography, just like encryption is a subset of cryptography? Wikipedia says (to me) that signing is not encryption: "In cryptography, encryption is the process of encoding messages (or information) in such a way that eavesdroppers or hackers cannot read it, but that authorized parties can." Encryption,
per se, seems to be the opposite of how the blockchain works (everybody sees every transaction).
That is not a good definition, encryption is basically just a mathematical function that takes plaintext and a key as inputs. With public key cryptography you have two keys and what one key encrypts the other key decrypts.
What we call encryption means using a public key to convert a message to cyphertext. Signing is the exact same mathematical function, except the private key is used and the data which is encrypted is the hash of a message instead of the message itself.