Sharpening a real Forstner bit isn't something easy to do. The above shown video is clearly good for sharpening what used to be called a multi spur bit. It seems these days the descriptors for consumable wood boring tooling gets a little vague. Below are annotated examples of what I knew as a Forstner style bit. They aren't easy to sharpen at all because the inside of the outer edge has to be ground sharp.
Tried to do my cheap "Columbia" HF specials. Took some work as the flat edge is a single bevel. Smaller ones are smooth rim, so quite difficult. Bigger saw-tooth are easy.
I use these for "ugly" work. I bought some good Fisch bits for good work.