There is no reason for him to do so apart from keeping the volume high but then again PrimeDice got alot of high bettor daily that wager alot and it is highly unlikely that Stunna needs to manipulate volume.
Aside from that he got profit even without betting so there is no point for him to do this plus he got tons of support mail to solve  . Apart from that Stunna is not the only "share holder" of PrimeDice so if he lose then he is not getting everything that he lost back to his pocket.