Their KYC request is not a problem....
Every site has their own set of rules, I'm a user of Kucoin as well, I started with my account unverified but later I was able to verify it to avoid problem like this. Since you said KYC is not a problem, why not comply with it and if they will still not release your funds, then you can make a scam accusation against the site.
So it is okey for you, an exchange to suspend a users account without even notifying him. I don't know, it is not for me. I am not doing scam accusation. I am just showing the value given to users like me by Kucoin exchange. I can't imagine such situation happening me if i was someone who doing high volume in their exchange.