Ash certainly knew.
But he really didn't expect that Rose would be willing to save the cage imprisoning her. She clearly understood nothing, not even the concept of good and evil. Her existence spanned an unimaginable length of time for Ash, yet her nature was even more innocent than a baby.
Because Ash was special, she followed him, and because she was an assistant, she would do whatever Ash asked her to. Ash would unconsciously rely on her abilities but also wanted to care for her naivety.
Before the Holy Grail was separated, Rose said she felt terrible, an agony even the Source Angel could not bear. No one could imagine how she, in such a state, distributed her power to Allstars. Perhaps it was because of Ash, perhaps an awakening of kindness, or perhaps her deep love for the beings of the Void Realm over the millennia.
But in this way, could Allstars—
