Sometimes people have incomplete files that are a part of Partial File Sharing. This probably didn't apply to your scenario but just a thought. I know I've sometimes been surprised at sharing a file that was not in my library (ie: saw people uploading such files in upload window).

It seems I cannot share ANY of the video files/folders I have without sharing ALL my video files AND any new downloads regardless of what folder I save them to (even UNshared folders!)
4.18.8
(tools>opitions>shared folders)
I have ONLY the folders in the share box that I want to share.
(Under legend) Folder is fully shared including all sub folders. THAT IS NOT AN OPTION AND CANNOT BE UNCHECKED.
And below that, it's either:
Share new downloads to unsaved folders OR
New downloads saved to shared folders will be shared. (Both are the Same thing, no?)
Partial sharing is not checked, btw.

The only way I seem to be able to keep it from happening is to NOT share ANY video folders/files and to disable ultrapeer.