Ironically, encryption is not an important part of bitcoin (?)
Cryptography and Encryption

In the wider world, cryptography is used for a variety of security related purposes:


Authentication (proof of identity, or proof of ownership)
Non-repudiation (author cannot later deny authorship of data)
Confidentiality (secrecy - third parties can't see the data)
Integrity (proof that data has not been changed or tampered with)


When we say "encryption" without clarifying further, we are usually talking about the use of cryptography to ensure confidentiality (secrecy of data, but not secrecy of a transmission having occurred - the latter might involve steganography or private channels etc).

Bitcoin's peer-to-peer protocol doesn't need secrecy but it does need a form of authentication and integrity proof that is provided by digital-signatures. 

Traditionally digital-signature algorithms used RSA which involves encrypting a hash of data but not encrypting the data itself. Bitcoin uses Elliptic Curve cryptography which produces digital signatures without involving encryption of a hash.

So the author is perhaps pointing out that the data sent by Bitcoin peer-to-peer protocols is not encrypted for confidentiality and does not involve encryption.

Terminology

The word crypto-graphy literally means hidden writing. There is a certain irony in using this term for elliptic curve cryptography which cannot directly be used for hiding the text of messages - what many people mean by encryption is the process of converting normal readable plaintext into unreadable ciphertext.