The main purpose of a frog is to remain attached to the belt, thus allowing the sheath to be inserted or removed as required. Also, knives have sheaths, swords have scabbards.
Ha. I found this video because I was searching for more information about what a "frog" on a scabbard looks like and how it's installed / used. I learned that term today from a post on Bladesmith's Forum about what I would call a "tusked tenon" tang, and what the poster called a "jamb knife." And then I see you put the handle together with that wedge, and I was like, "Ah. Same guy." Am I right?
I arrived at the idea of a tusked tenon organically as I'm getting ready to make my fist knife (farrier's rasp seax / camp knife), and wanted something for handle assembly that's presumably strong yet within my skillset as a woodworker, but I don't have the time / material to experiment with something like that if it's a novel approach. Then I found that BF thread, and it was a huge relief to see someone had already tried / perfected it. I admire your work and appreciate you sharing your process.
Very nice work. It is a good idea to ruff up your leather a bit before you glue it. Use some 100 grit sandpaper. That will help the glue to be stronger when it dries. Your work looks just fine.