I would like to know if their "provably fair" mechanic is actually NOT fair, but just too technical for the layman to understand or actually prove.
I believe a lot of users misunderstand the meaning of "provably fair".
It does NOT mean a guarantee to win, it does NOT even mean a guarantee not to lose.
If I make a lottery where I announce ZERO winchance and then I make a random generator that rolls 100% losses, that's still "provably fair" because I can prove that it gives EXACTLY the winchances announced in the rules.