They are cable splitters when they are used normally on a Rohloff hub with internal shifting mechanism.
For use elsewhere, they are wider than the alternatives (screw up action rather than twist and remove) I used on a splittable Moulton I once had, so I reckon they are less suitable as more likely to knock against frame tubes. Also probably more expensive.
But they should work OK for gear cables.
I wouldn't want to use the Rohloff bayonet connectors for brake cables.