What would you say if RHaver play at Bab? Yes of course he win he know the "outcomes" becouse he have the last Hash as Dev

this only as a tip.
The reason I don't play at BaB is not because I can look up the outcomes, it's because I'm 100% of the bankroll. That means no matter how much I lose or win, I will lose or win exactly 0. This would serve no purpose other than to inflate stats (and mess with the bonus pool), so I consider it improper.
However, in MP's position I don't see anything wrong with them gambling on the site, as the wins and loses would be real and serve more than stats-inflation purposes. The truth is, if they were going to cheat they would just cheat (and use different accounts).
I actually remember once on JD dooglus gambling, but (my memory might be wrong on this) to reassure investors he told everyone exactly how he's going to gamble (a bet low, martingale sequence until he got to X or busted Y?) and got users to call out the digits in chat he would use as his client seed. (or something like that). It's not the most robust way to do it, but I don't recall anyone had any issues with it.