You're right, and I did consider it, but in the end I decided that angling the ends inwards as i have done will also spread the stress across a number of grains, much less likely to cause a fault crack as on the Right Hand Side of the picture below. Also the grain of the patch is very slightly offset so it doesn't run parallel with the top grain. Feathering the edges is
quite a bit more work.
in fact you can see in the original repair, the left hand edge is still quite sound; it is angled. The right-hand edge however is parallel to the grain of the top and right alongside the saddle cutout - recipe for a weak point and a classic saddle crack, which is in fact what happened.