Its good that OP didn't provide any good proof for his claims.
The BJ on bitcasino.io is not provably fair, and the problem on not provably fair sites is that there will never be good proof. The site cannot prove the game is fair, and the player cannot prove it is unfair even if he is having an unlikely bad run. I do agree with OP that people should stay away from the site and any not provably fair sites.
But you should know that "provably fair" is only the concept in BTC gambling industry, in fiat world, never seen this kind of concept before, so casinos use those famous fiat game providers like betsoft, microgaming, net ent and so forth, it is impossible to prove it is fair or not.
For my experience on betsoft BJ, IMO it is fair cause I bet 3 btc per hand for 3 times, I won 2 times and lost 1 time, if it is rigged, how can i win 2 times? I should have lost all of 3 times if that is rigged and unfair.
BTC gamblers should follow the trend, it means that provably fair is good but
not compulsory in the industry, we can't force people not to play those famous casino providers' games.