Please for the love of all things holy. Do not do not do not put this game on the Epic Games launcher. That is all. Thanks for reading.
Edit: Woot first post!
I have no problem with Epic Games launcher and in a lot of ways it could be good for consumers to have some competition. But exclusively on Epic Games launcher would bother me a lot. I happen to prefer steam and so while I still think limiting to one platform is bad it would bother me a lot less if it was only on steam.
I expected it would be a VR direct client and I would consider this normal and acceptable. Even when MMOs are on steam they just open a launcher limiting the advantages of the seam client anyways.
Third-party launchers introduce things beyond VR's control and if they keep other things running in the background add lag and chances for crashes. If they do *not* keep other things running in the background they add no value to the player.
The only reason to use them is in order to better market through the third-party, in which case they should be an option for those who buy through the third-party and under no circumstances required for the rest of us.