I have already posted here a few times about my opinion that a contest where the only prize is publication, is not a contest. Even if you "win" an advance on royalties, because that money is not a "prize"--you are going to earn it. It is no more a prize that a cash advance loan on your salary is a prize.
In my opinion the problem with calling it a contest is that it can bypass the part of your brain that says "do I want to submit my manuscript here" or "is this the best place I could submit to?" And if you do want to submit to this publisher, you are doing so in a way that maximizes competition and possibly associated delays.