All I will say is that I strongly oppose "Bonus" as the title for this pack or any of its subfolders. I know we had this discussion already in NL, but there it was my decision so I didn't feel obliged to lay out my reasons
This folder contains levels from various versions of
Lemmings, such as "Going Their Separate Ways" from the Mac version. In their source games, they are regular levels that you would encounter in the normal course of play just like any other level. Granted, they have been regrouped in NL (and SLX) because the main Lemmings / Fun, Tricky, Taxing and Mayhem folders contain only the Amiga levels, but they are
not bonus levels.
I don't know if I ever made a final decision on the folder name for these levels in NL... currently on my installation the folder is "Misc Levels", which is okay I guess.