Whether there is any truth to that or if one can even tell, I couldn't tell you.
You can't deny the physics, but...
I shoot Skeet doubles with the lower barrel first and Trap doubles with the top barrel first. The Skeet gun is a little heavier and the trap gun a little longer and, as my friend 1-oz speculated, I don't notice any difference. Perhaps if I were shooting boomer duck loads, I'd notice a difference.