Epic makes games, and licenses their tools to make games to other people who make other games.
A conflict of interest is inevitable. Apparently, considering the number of their licensees, nobody has much of a problem with it.
We haven't had a situation like this where games of the same genre are competing within the same timeframe. Add to that the genre is still relatively new and up for claims by the AAA space.
I can see Epic taking strategic decisions to delay addressing engine specific issues in order to promote their product first. Not saying they have, or they will, but the incentive to do so is definitely there, and Bluehole have good reason to be uncomfortable with this relationship.