Why is the Night Fision front blade wider than the rear notch?
For a more precise sight picture at distance.
You still get light on either side of the front when viewing through the rear, but the narrower the light bars, the less room for error side to side.
There used to be several sight sets available where the rear notch was the same width or narrower than the front. The only other sights I can think of off the top of my head now are the Haley Strategic Thirteen sights for Glocks.
I'm actually very excited about these sights!