Tabbed case detail

FB129673

Technical spec: https://confluence.dimagi.com/display/ccinternal/Tabbed+Case+Detail

Not-so-technical spec: https://docs.google.com/a/dimagi.com/document/d/1MiGqDJA59ZN9ycEWuq5ObVc9lhpVe0TgwCAfInhDzF8
I'm curious about why this is a custom class here, but not the tabbed_detail_view below? I would have assumed that a tab host would have worked on both?