Not using a passphrase decreases the complexity and points of failure of the setup, which he values more than outright security, since a complex (secure) setup is useless if you forget or lose access to the details, and is best left to advanced users, or the company he works for - wink. 

He's writing to the masses, where an XOR'd set of seed words lets you have a simpler setup, easy to restore, and also includes plausible deniability since each of the XOR seed plates is a valid set of words by itself. An attacker has to know it's one of a set to know there's a larger wallet elsewhere. 

The seed+passphrase setup is similar, in that you can load funds onto the seed-only wallet, and you keep the passphrase safe for the "real" wallet. But an attacker now has your entire seed phrase.