The main problem of other sports betting site is that when a player wins a big bet ,and after that when he try to withdraw it their the problem will start and the user will get all sorts of problem. That is the main reason Directbet got success because they had limit on each bet to maximum limit so that user can see according to it and bets it. Their are so many scam issues against lot of sports betting sites of not receiving withdrawal problem.
You seem like you're talking about sportsbet.io.Yes they're scammers,if you win a big bet they would ask you for KYC and all the other formalities that doesn't matter.It's ironic they go for the legal ways when they're running a false casino.End of directbet was end of sports-betting for me.Still couldn't find a single website who'd be as enhanced as them when it comes to sports betting.
I think its normal when a betting site ask for KYC documents of their customer. Usually it happened on first time withdrawal, it doesnt matter you win big or small.
Its a policy of every online gambling sites, just to ensure that their customer do not cheat or one person open several accounts. Moreover, its to ensure that their customer's account is safe, who know if their account has been hacked and that person proceed to withdraw all the money.
just my 2 cents