Yes, for example Youtube video links are copied with the &pp= tracking information. Search for something on Youtube, right-click on a result title, and copy with or without tracking gives you the same thing (with the pp=).
That feature removes parameters that are known to be used for tracking. It does not remove all query parameters willy-nilly. For example on youtube it should remove si, feature and kw parameters as well as a set of parameters on a list that applies to all websites. However, pp parameter is not in that to-be-removed list.
As an example v parameter is for video id on youtube, it would be kinda silly if that was removed, so the feature kinda has to do some site specific action.
For me neither. I use it out of habit instead normal copy. But it never did anything for me. I have couple of security and privacy extensions installed, so I thought maybe one of them gets it in the way for some reason.