Op if you don't play at betterbets then there is a motive behind your post. I'm going to guess extortion probably. This looks like some kind of oversight error. They fix it in minutes....now we can pick client seeds in the 4 billions on accounts. So dev said they spoke to you and it seems outcome wasn't what you wanted -gimme money or I'm posting- and you made this post. Does this about sum it up?
They fixed it mainly because he contacted them and asked about this issue. Without him we probably wouldn't be aware that exploit like this can be even possible.
I don't know if he demanded money for this, but if I were the owner of BetterBets.io I would honor Op with some kind of small bounty for his bug hunting.