I would say that to read the relevant verse from Hebrews as making an ethical and metaphysical statement about the nature of Will, the relationship between potency and act in God, etc is to ask too much of it.
Hebrews says, He cannot lie (It IS Hebrews, right? whatever...) I say Lying is not a thing about which "can" or "cannot" can strictly speaking be used. Better to say that someone who lies cannot tell the truth.
It's the whole evil as a privation of good line of thought.
Do you ever read what we write?