Clearly this all boils down to simple physics. If you have a scratch you will have to remove material until the lowest point on the scratch is gone. What is in the video is a scuff (grouping of small superficial scratches). I think this is where PolyWatch really shines (no pun intented, but I'll take it). For a real scratch that has some depth it's going to take a long time or something more abrasive.
The simple fact that Polywatch leaves the watch "shiny" says that it has very fine abrasive qualities.
Just for the record, I have my tube on stand-by. Have not needed it "yet"