No backdrops in mixed library overview

[zelpi]

The background of the Movies and Shows library overview displays automatically backdrops which are taken from the detail pages. 

I have a mixed library where this doesn‘t happen, the background of the overview remains black. Is this intended or is there a way to also activate in this mixed library backdrops?

[TheDreadPirate]

Not sure if this is an oversight or done on purpose. The backdropContainer <div> is empty for mixed libraries.