Because the zone is listed to be served. It is then available straight
away, with actual authority queries and answers.
The other configuration, where the zone is used to speed up processing
(root copy set up), is not, I thought, as straightforward. So I made
the one I thought was more straightforward the default. I.e. loading a
zone for authority service without other config, is that. And enabling
the hyper-local root zone, needs some option to perform the local loop
portion.
So, I thought it would be less 'surprising', than local-loop processing
only, or not using it for local-loop processing either.