bucket_uuid part of service creation rather than service binding?

I might be missing some understanding about riak, so I'm sorry in advance.

It looks like the unique bucket - representing the service - is created during binding time and not during service_instance creation time.

Does this mean that each binding gets a unique bucket to write to?

If so, I think this isn't correct. I think there should be a 1:1 mapping between service instances and riak buckets; not bindings and buckets.

A binding represents an end user (application) that will be granted permission to access the service instance (bucket).

Or does a single riak only have one bucket and this broker allows binding to it?