Earlier quoted context omitted.
No. Your buckets should be private, with a security rule that they can only be accessed by your CDN provider, precisely to force the CDN to be used.
Why isn't that the default? I'm glad I use a Hetzner VPS. I pay about EUR 5 monthly, and never have to worry about unexpected bills.
The real question is if they considered caching and thus configured it appropriately. If you don't, you're telling everyone you want every request to go to origin