First of all, I agree this is all bananas:-) but it seems is the same with GCP and Azure. For Backblaze B2 it seems its unclear in the documentation. Willing to be corrected on this....
> Generally, you are not charged for operations that return 307, 4xx, or 5xx responses. The exception is 404 responses returned by buckets with Website Configuration enabled and the NotFoundPage property set to a public object in that bucket.