from what i understand, yes it'll bend the valve(s), because the timing belt isn't turning the cams, due to this the valve(s) wont move. but the cylinders are still active because its on the crank. as the engine tries to crank it'll turns over moving the cylinders up and down, if the valve(s) don't move along with the cylinders, it'll get hit causing the rod to bend.
that's why you don't crank the car after a timing belt snap.