On a MacBook Pro10.12.2 I recently ran erase free space 35 pass. being curious I ran data recovery after that and found 100's of deleted files of all file types.
deleted documents, jpeg, tiff, png. gif all the image file types. all the video file types. Also web archive and zip.
There were about 700 recovered jpg. many videos and documents from the past.
Many of the files are 'system' content, others, jpeg and mpg are things I have never seen before. Some of theses may be "system" or some part of iMovie, one - three second second videos.
The remainder was all deleted items I recognised, many business documents, family photos etc.
So, what is a 35 pass erase free space if all this material is still there?
cheers and thank you in advance
P