The video makes a real mess of getting into the back cover and then bends the battery! Not a good example.

Also, I would say a guide that says "watch one of these YouTube videos" is not a great guide.

I also broke a spudger trying to do this. Eventually I figured out it is easier to go in diagonally from the corner, just to one side of the screw hole, and lever until you hear the adhesive pad tear and give way.