Mooooooney.
Incindentally, I get the feeling this will mean higher prices consumers pay on the game. PC usually has options where you can pick up pre-orders 20-30% off. But I wonder if that will still be the case now with Epic only titles.
The advantage of steam is you have massive eyes on. So yes you're paying for a premium, but it's because it can direct a lot of attention to your game. I wonder if they really think the game is big enough in terms of interest they don't need that. Having both makes sense. Epic only. Seems odd.