It looks like you're flagged as a winning gambler. Some sites limit players and/or ask for KYC faster than others. I'd assume that's why you ran into problems with Stake, Sportsbet and Bitsler. Thanks for bringing your experience to the thread.
I have never heard of such a practice. If anything, limiting players for winning too much sounds like something which should be banned under regulation laws for online gambling casinos. Because that sounds very messed up, and if anyone can prove they do that then I imagine a lawsuit would not be far off. But I am no lawyer so perhaps I am wrong.
But what I do know is that if you are planning on gambling on a KYC casino then it is smarter to do KYC before you even deposit funds into your account. That way they cannot withhold your winnings from you for a long time on any verification grounds. Otherwise they can "verify" your documents for ages and you could not do anything about it because there are no rules on the time limits of how long KYC must take.