The Epic First Run programme allows developers of any size to claim 100% of revenue if they agree to make their game exclusive on the Epic Games Store for six months.
After the six months are up, the game will revert to the standard Epic Games Store revenue split of 88% for the developer and 12% for Epic Games.
Epic complain because it doesnt benefit them. If they were the one with a large ecosystem, you bet it would be closed down as much as possible. Fuck Epic games, shitty company.