Ref issue 75489, what is intended purpose for the "non visible" buttons that now show on context menu of each toolbar?

Here is a mixed UX and Dev question... 

As submitted by a vigilant user,  "OfficeUser" (Norbert N.), <a 
href="https://bugs.freedesktop.org/show_bug.cgi?id=75489";>fdo#74589 </a> raises an interesting UI 
question, introduced for 4.2,  what is intended purpose for the "non visible" buttons  that now 
show on context menu of each toolbar?

Through the 4.1 releases, toolbar context menus provide only the 'visible buttons' and 'customize 
toolbar' (as well as dock, dock all, lock, and close).

With 4.2 we've added a function to show on each toolbar's context menu those buttons that have NOT 
been selected as visible for each toolbar. 

Also,  these buttons on the context menu show as active, and take a button click. However, they 
seem to not have been connected to any action.

Same behavior for all  the 4.2.x builds, as well as for 4.3.0 builds of master.

Did something not get finished, or was just forgotten?   Seems we should either complete their 
implementation, or could set them unclickable, or even remove them as a UX distraction.