The one in my parts box came from a TR4 with OD, so the factory apparently used them there.
What I've heard is that it was part of various attempts to eliminate 'buzzing' of the gearshift knob at certain speeds/rpm; which became much more noticeable with the longer TR4 shift lever (and perhaps the slightly longer 4 synchro gearbox). The brace to the shift extension was supposedly added for the same reason.