Garrot looks unconvinced that the monsters are unable to choose. Those were Ten's direct words, after all! But there's a lot he doesn't know about the monsters and how they work.

Luka's question stops all of that dead in its tracks though.

"Why do you think he did it?" The insight might not matter, but with what Gyre and Luka shared and what Garrot knows, no motive will bode well for them all.