JavaScript enabled tab interfaces - is the ability to use dropdowns useful?

Currently the dynamic javascript enabled tab navs http://v4-alpha.getbootstrap.com/components/navs/#javascript-behavior allow for the use of a dropdown.

This particular use is fairly non-standard, and from an accessibility point of view this impedes adopting a "proper" tabbed interface pattern with correct role="..." etc https://www.w3.org/TR/wai-aria-practices-1.1/#tabpanel as that pattern does not foresee anything other than straight "tab" triggers.

As such, I'd like to get opinion from implementers about whether or not they find the current tab with dropdowns useful, or if dropdowns can be removed (which would then allow a proper ARIA tab implementation).