I use decent brass, so I dont do anything like sorting it, and I never touch the primer pockets or flash holes. I keep all firings together so they all age at the same rate.
I measure headspace and shoot in order of variation, but thats normaly only 1-1.5 thou.
I sort my bullets and point.
I measure power to 0.04 so if Im wanting 44.0 Ill allow 44.00 and 44.02 - not 39.98 or 44.04. Does it make a difference? Probably not! Does it do any harm - definitely not so why not do it, its another thing to eliminate.
I seat to approx 1 thou, and make sure all neck tension feels the same - anything thats an anomaly is a blow off.
Can you get away with not doing this, probably - but after 600 yards, everything needs to be super consistent and if it makes no difference but mentally eliminates any doubt its worth doing.
This video is good