Book navigation position cannot be changed (is always at bottom)

I know you need to activate the full display to show the book navigation in the Field UI, this works.

But when I move the book navigation field up in between some fields so it is no longer at the bottom it stays at the bottom in the final output.

This issue has been mentioned before in https://drupal.org/comment/6755190#comment-6755190.

A workaround that works is to wrap the book navigation field inside a fieldgroup and move the fieldgroup.

Marking this as minor because it is probably a rare use case with an easy workaround.