The phrase "one of my accounts" should be interpreted as an account opened at Cloudbet. I can not say if I have opened an account at Cloudbet before the day in question prior to 2018. I began keeping better records and can say that I have not opened an account since March of 2018.
An account opened at Cloudbet does not eliminate the possibility that there was
another account in the past that you forgot about. Like you said, you only started keeping proper records in 2018. Based on Cloudbet's reply, they did suspect that it was a matter of multi-accounting. And those things can happen if you are using VPNs.
In the end, it looks like this will end on a positive note. Nothing has been proven and the bookie has decided to settle the matter.
I do not dispute the possibility of another account, but I sincerely do not know if I ever made one prior to the account in question. I can't go in to much detail about my tooling much like I suspect Cloudbet won't want to go in to much detail about how their risk detection system works, but I can say that with high confidence, regardless of how much telemetry Cloudbet collects, the machine and individual Cloudbet saw that day were brand new. It's very likely that the only thing that triggered the KYC request was the use of the VPN. We're getting a bit off topic here, but if that's wrong and Cloudbet did not see that visit as unique, I would happily take that data in lieu of the 0.005 BTC refund mentioned upthread. To be clear, that's not a challenge or taunt, I truly am interested and would love the opportunity to improve my methods. Cloudbet, please PM me if you want to pass that info along instead of the refund.
Cloudbet has processed a refund as discussed upthread. I've withdrawn my flag and revised feedback as agreed.