Even if the distance is not the same, they may function better with both sub's phase control at 0. The avr may use an average distance of the the two sub's in it DSP calculations. Also the physical and acoustic distance are not necessarily the same thing.
Klipsch RF 7 based HT 7.4, Pioneer SC 35, Acurus Five 200 amp, Chase SS 18.2(2), VS 18.1(2), Samsung BDP F 7500, Asus/My Book Live HPC 4 TB
Yaquin VK 2100 amp, McIntosh XR 5 speakers, Samsung BDP F 7500