Baluns and other circuits in The Duet

When I removed the power device I noticed there was a balun between the 2 Power outlets and there was an additional balun dedicated to the Power Port on the outer one. I think it’s reasonable to assume the balun circuit between the 2 outlets that prevent the digital circuits from contaminating the analog AC power. The balun dedicated to the outer Power Port is what has me scratching my head. Is the outer port that needs more filtering due to digital contamination?