by Ken Task.
Have searched a DB of a site that has embed YouTube videos and indeed that does not copy the video to Moodle - can't find any references to them in mdl_files.
So the links that went to local videos ... are they deleted? or hidden? Hidden would mean, I think, Moodle never deletes ... still linked.
One way to see what's in the backup ... download the backup to a test directory, change the extension to a .zip, and unzip it. If the videos are there in the backup they would be in files directory but with contenthash names. Use the files.xml file to x-reference what contenthash named file (and location) is a video file found in the files directory.
'spirit of sharing', Ken