I kind of was wondering about that my self. I could pull the engine forward with my bare hands once the dogbone engine mounts were removed and it was in park. There was a big sticker on the tool saying make sure the transmission in in neutral when using this tool. No explanation was given. This tool can be used on more than GM cars. It comes with a little extension which replace part of the front dogbone engine mount for use on GM engines. Could be this is a cover you ass warning since damage may occurs to other make cars.
Like your pry bar method.