That's a very good question. My performance mal paddles better fin first as the nose area makes it easier to catch waves

I reckon it's purely to allow for nose riding and glide. If you reduced the nose area you reduce the glide but you reduce the swing weight to so it might turn better, quicker.
But would it become a stretched short board with less glide and wave catching ability. It would look like a rhino chaser. I haven't had a problem with the nose catching unlike some wider nosed short board which seem to catch on the down or straighten out turn. Not the katana but

Deano