I have made "long filler" bouchons of several pipe blends of whole leaf tobacco (not Semois), and have the impression that all it does is allow you to prepare multiple pipe bowls of tobacco ahead of time. You just stick one into a pipe bowl, and light it up. I detected no impact on the taste or aroma. I think that creating bouchons at home is a curious exercise in odd traditions, but otherwise not all that meaningful.
Bob