I also think it's nothing more than just an advertising trick because OP shared only his winning transaction, in gambling everything form is risky even 0% house edge gambling form too, we can see this how risky that is too like someone place money on block 433141 and lost there.
Yes i agree that it is just some advertising but i dont understand why someone would posts their lose? Doesnt make sense to me, all we need is just big win to make sure that their site doesnt cheat like some other site. And this is gambling without high risk you wont get a good payout, in gambling you risk everything to get more so i think it still worth it