It wasn't being thrown into the fourth dimension and it wasn't whatever. His physical body was destroyed. That's explicit in the text. So he's proof that consciousness can survive the total destruction of the physical body housing that consciousness. That's a pretty good working definition of an immortal soul.
You actually might have a better argument with the iron age Bates/Weisman Cap than with the Silver Age Gill/Ditko version or with Dr. Manhattan, since there is the implication (incorrect in my view) with the Bates/Weisman version that he was just catapulted into the future, not atomized. Except then you have stories like this.