I am still using V12, (can't afford to upgrade and haven't found a reason to yet) and I have been using Vegas since V2, but I never noticed this before.
If you open a clip from the media pool in Trimmer, you can open another project and the clip is still in the trimmer. You can then trim it and use it in the new project without having to import it as media. Not sure how useful this is in normal circumstances but I found it curious. Does it still do this in V17?