The Strong Side/Co-Ordinated Side forward is a staple of JKD that is actually shared by a lot of MMA trainers. Mark Hatmaker (author behind the No Holds Barred Fighting series of books) states that since the variety of attacks and defense in MMA is so vast, a Co-Ordinated side forward lends itself well to attacking, defending and countering. He also states that both would inevitably be trained/drilled in the chance that you aren't able to set your feet correctly, or if you get turned. "Inevitably" being stated as it is best to become familiar and skilled with what you feel most natural with.
Myself, I spar in a southpaw stance more often than not. I find that is the case especially when I know the person in front of me isn't a strong grappler. I find it's easier to get a hold of a person with my right hand leading, and also I get more power driving out of the bottom of a duck walk with my right leg. Further, I'm not disappointed with the amount of power I get from my left side being back, as there is more than enough distance for the strinking limb to accelerate.
In either case, repitition, repitition, repitition is key.
It doesn't matter if you agree or disagree
... As long as I don't bore you and I spark a moment of thought, my goal is achieved
Queng leon queng tigre ecu tacacut, queca pa? - Pampangan Mandarigma Motto