a. we haven't any proof for this except some pictures or videos that show someone has high chance .
b. if Robbinhood could find seeds , why stunna couldn't do that and manipulate our bets ?
Either of these events , stunna is loser , in option a stunna cleaned up robbinhood's profit for no reason and in option b stuuna gonna be unreliable
You seem confused about how things work.
Stunna paid HufflePuff over 2000 BTC already. He has nothing to gain by announcing the HufflePuff was cheating. It would look great for the site if someone actually won over 2000 BTC fairly and got paid out. It would give other plays hope that they could do the same. Announcing that the biggest ever winning did his winning by cheating doesn't help Stunna or the site at all, and so it is very likely true.
Stunna of course can see everyone's seeds. He can't manipulate your bets due to the way that the site's provably fair algorithm works. If he tried, he could be caught, and publicly outed. It's not worth the risk. The only real risk is that he could make an account and play on it knowing the seeds, and use the seeds to win. But he would only be winning from himself (and his private investors, assuming he has any). It's not a concern for players.