Website is shady afaik even Hufflepuff managed to scam PD -they finally figured out how this was done. Point being, there IS away PD can screw you if they chose to reverse engineer the Hufflepuf technique. I am sure they were aware of this long before. It's as soon as you start playing big bets the system gets you.
I read about this Hufflepuff "incident" and I don't really think there is anything to "reverse engineer" for PD as his method simply exploited some kind of server weakness, if you choose your own client seed everytime & verify our bet everytime I think you're safe, I remember another casino accused of cheating and even there if you use own client seed and verify every bet they can't cheat you.
Its pretty much next to impossible to reverse engineer an provably fair system. Yes they give you the hashed SHA256 seed, if you could somehow find the unhashed seed then you would be able to know the outcome just by adding your client seed and noonce. This is currently not possible. If it was then the entire internet would be a security risk.
My guess is he found some leak of unhashed seeds or he determined maybe some deterministic pattern into how the seeds are generated.