I have not checked their Terms and Conditions about why they would like KYC to be sent before closing an account but when customers usually register on online gaming websites or casinos they accept a whole range of conditions and many include the asking of KYC as and when they deem appropriate.
I do not know about what happened in your case therefore can you explain if they wrote to you to explain why they declined your documents? Also, as this is something you are claiming without providing evidence, are you able to provide any evidence that supports your claim because until/unless you do it will be difficult to believe you.
I asked BC.Game to close my account and let me withdraw, they said they couldnt without kyc first. Been trying to verify, have sent all my documents, all of them coinciding since im a legit person obviously, and they havent been good enough to let me verify as of yet.