What has to be explained is the more detailed story on how did he manage to get his own seed. The server seed is never revealed to the gambler until he changes or resets his seed. But in this case hufflepuff managed to figure out his seed in some way.
If two accounts had the same server secret for some reason, you could reveal the secret on one account, and play using it on the other account. That may be what happened, but I don't think it has been revealed yet how anyone would get the same secret on two different accounts.
The problem with that assumption is that there will have to be 3 accounts with the same seeds to make sense of that theory. At the end Robinhood clearly showed the advantage he took of the flaw by winning many 10 BTC bets. So he probably didn't reveal the seed on that account, as he knew the rolls.
HufflePuff happened before this, and since its believed he had the seeds on that account, so probably there might be a third account where he got the seeds originally, at first from .
Or perhaps he had 2 separate pairs. If he managed to get seeds off 3 accounts, then there definitely exists or existed a flaw. I wonder why Stunna still hasn't commented on it.