Jeff is just filling in the hook. By laying a straight edge on the bottom of the boat you can see how much is there. On my 23 resto I ground out the back trailing edge and then filled the rest. Since Jeff isn’t doing the floor again he can’t add additional layers to replace grinding some out. He is just filling it to get it flat/ straight. Think of hook as a built in trim tab. He is also extending the center 2 strakes all the way to the transom. From the factory they stopped about 18” from the transom.
First step was remove gel coat to bare fiberglass. He is then using fiberglass filler( kitty hair). Then finish with regular filler (think bondo), epoxy prime, and paint/ gel.