I think there should be not an issue if you do the KYC before the casino blocks you withdraw and ask for the KYC. Infact to be more realistic, why not do the KYC before even depositing at the casino, so that in case the casino do not accept your KYC for any reason, your funds are not stuck there.
The only exception for those casino that do not have any KYC compliance and you will not find any link to do the KYC. Rest if there is a KYC link, better do the KYC first and then deposit to gamble. Also, i do not recommend, going on the news site and do the KYC and gamble. Better stick to already established ones, so that you are confident to some extent that your KYC data is safe on the site.