In order to make our Object Storage API as close as possible with AWS S3 one, we will soon modify the create-bucket command behavior.
In 7 days we will deploy a new version of create-bucket that will return the BucketAlreadyOwnedByYou error when you call it on a bucket that already belongs to your organization.
If you have any custom API client relying on the absence of the error please update it as soon as possible.