I do think that a lot of these sportsbooks don't make it clear that people need to pass KYC before they can withdraw, which results in a lot of people having these issues when they do try to withdraw. If they require KYC, then they should make it clear when you deposit that you are expected to complete KYC, or better yet, conduct KYC before you're allowed to deposit.
It's shady how they selectively "verify" those who win big amounts, and hold onto their funds for long preiods of time knowing that they would most likely not be comfortable with providing ID.
Also, I don't know why they are asking you KYC for a second time. Once should be enough. I wouldn't trust Sportsbet.io personally, tbh, because of these policies that they have.