By that time in the game Shanoa already had absorbed all three Glyphs. But knowing what Albus had said about using Dominius Shanoa chose not to go through with it, and then explained to Barlowe why that was the case. It was then that he lost his s**t and we know the rest.
I knew I'd remembered that correctly. All 3 glyphs were already absorbed, so shit was about to go down either way.