I looked at BetKing's provably fair implementation and determined that they can use shufflepuff as an exploit AND their shuffle algorithm has a modulo bias. In general, for an eight deck blackjack game, the modulo bias occurs once every 200,000-400,000 hands. Not a lot, but easily fixable. To fix the modulo bias, BetKing would want to discard any number n where n >= MAX - MAX % modulus, where MAX = 2³² - 1.

A good thing about BetKing is that they keep their code simple and easy to read. This is in contrast to some casinos that have very complicated methods for similar functions.