At 4" behind axle, for every 1000# of GN tongue weight the front axle carries 25# less weight.

With a gas engine factory front axle is approx 3600# and diesel is approx 3850#.  With an extreme case of 4000# pin weight makes the front axle 100# lighter, which still leaves a Duramax with more front axle weight than a gas engine model.  It realistically is not noticeable and significantly reduces the chance of a cab strike. 

Now compare to a bumper hitch where the receiver is 52" behind axle on long bed and 50" behind axle on a short bed and the ball is another 6" back.  On a CCLB every 100# on the receiver ball removes 33.6# from the front axle while a CCSB loses 35#.  A light 3000# trailer with 10% TW removes more weight from the front axle than a 20,000 GN trailer with 20%TW.

Long story short: it's not an issue.