Acoustic Guitar Construction

Every article, thread, etc. I see about leveling frets before dressing uses a flat leveler (file, board with sandpaper,etc). What is wrong with using a radius block with the same curvature as the fretboard?

The long flat abrasive is knocking off the high spots averaging the surface not creating a radius that work is already done --- like a rotory lawn mower or deck with its flat blade/s on a slope. Plus the chances of having a contoured sanding block that matches the fingerboard radius plus the frets is zero. What happens is that the contoured block knocks material off the ends of the frets, both sides of the FB and you generally end up with a mess.