I feel like he definitely did die that way. Mace isn't flung out the window the moment the lightning hits him, but Palpatine keeps up a continuous stream of lightning on him until he dies. Which once he is dead and no longer in control of his body the force of the blast knocks him out the window.
The moment his body gets flung away is the moment of his death. At least that is how I interpreted it.
__________________ Chicken Boo, what's the matter with you? You don't act like the other chickens do. You wear a disguise to look like human guys, but you're not a man you're a Chicken Boo.