Isn't one of the advantages of the hybrid solid fuel / liquid oxidizer design that it can be throttled to some extent by cutting off the oxidizer using a valve?

Isn't one of the advantages of the hybrid solid fuel / liquid oxidizer design that it can be throttled to some extent by cutting off the oxidizer using a valve? I do agree that I can't see why a feather during a burn would ever be desired, but we'll have to wait for the NTSB to see whether the flaw was in the design or manufacture.