[Cryptography] Does this keying scheme make sense?

[John Levine]

I was talking to a guy at a conference who sells a package which,
among other things, encrypts files in cloud storage with each file
having a different key.  The keys are all generated from a secret
keystore seed in a way that is supposed to be secure.

I'm looking at his patent on the technique and can't tell whether it's
clever, or just overclever:

https://patents.google.com/patent/US9703979B1/

R's,
John