Originally Posted by
cyccommute
But, as with a star fangled nut, once the stem is tightened, the compression plug and top cap serves no purpose.
True. But a plug that has been pulled up accidentally will be an annoyance when you find the need to adjust the preload in the future. Until you notice that the plug needs repositioning and retightening.
An annoyance that is completely avoidable by using the compression plug the way it was intended.