Maybe, but it would also be very easy to blame on misconfiguration / mistake. Honestly, it wouldn’t surprise me if the behavior itself isn’t purposeful, but ignoring / not fixing it is. I’ve definitely seen such behavior at other companies, where they drag their feet on fixing a bug that is bad for the user, but helping them.
It was a server-side block, from Cloudflare (security rule specifically). I’m very familiar with it, having used the same service over a decade. They are able to tweak the overall security level, or specific WAF rules for the endpoint in Cloudflare. They also have analytics that will show them exactly how many cancellation requests would be blocked. The fact that they totally ignored these details in my ticket, is concerning.