Wow, that's a terrible argument. "Hey you used to have three+ places to buy this game that you were really looking forward to, now they're unavailable and you can only go to this one place to get it. They support developers, by giving them a larger cut, but you will still pay full price. Or you can wait a year for the game to be available at those other places. Don't like it? Don't buy it." That's not consumer choice. You really have no idea what anti-competitive means. There are many scenarios that describe anti-competitive business behavior and what Epic does with pre-orders is just one of them. Whether they remove the ability of one specific competitor, or many to sell the same product, it's textbook anti-competitive behavior. It doesn't matter what their public justification for doing this is, it's anti-competitive. There is no argument you can make otherwise.
You speculate quite bit without evidence. There are many people who haven't spent a penny on the Epic store, they just collect the free games. That's exactly what they don't want. There are also people who are going to buy a particular game no matter what, whether it's on EGS, Steam, Windows Store, etc. But there are also many people who now won't buy the game at all, pirate it instead, or will wait a year for the exclusivity to end on the EGS simply because they don't like what Epic is doing.