The carriers patented flared tail increase concentricty of the BCG within the bore of the upper. Angular movement of the carrier is reduced and bolt egagement with the extension is more consistent, which increases accuracy. Rounds are less able to influence the carriers position as they are fed from either the left or right of the magazine, which is an effect that has been demonstarated (in 3rd party testing) to shift point of impact, especially when more rounds are present in the magazine and pressure is higher.
The flared tail also limits carrier tilt which while more obviouse in a piston system is still a wear factor in Direct Inpingement driven weapons. In fact extreme carrier tilt wear has been whitnessed to remove enough material within the upper receiver to stop the bolt going into battery as the parts were out of alignement, this was observed in high round count (150,000+) range rental rifles.