Usefulness of "tabbar" options ?

I recently discover zathura and I enjoy using it.

After reading the documentation I found options for which I don't understand the purpose : tabbar-fg, tabbar-bg, tabbar-focus-fg and tabbar-focus-bg.

This suggests to me that tabs functionnality is implemented, but after some research it seems that it is actually not the case.

Have I misunderstood something ?

Thank for developping this software ! :)