The problem with a point of impact in action shooting is you need to cover what you are shooting with your front sight, trying to get 2 hits as fast as you can when you have the target covered is much harder than seeing where you want to hit sitting on top of the front sight. Plus if you get a stage with a couple 40-50 yard targets thrown in you have some over hold already built in.
As for the fixed sights, yes they would be much better for concealed carry and less chance of snagging but were talking about competition guns with many different types of people shooting different power factors with different weights of bullets and powders, there is a reason Tanfogilo and STI build all their competition guns with adjustable rear sights. A 9mm with fixed sights shooting POA at 20 yds with a factory loaded 115gr bullet will shoot about 5-6" low with a 147gr bullet loaded for IPSC minor power factor.