Let's approach the question with another question.............what was the overpowering reason for the front trigger to fire the right barrel on the first S x S guns? Or, why was it deemed more important that the right barrel be the more open choked? What wasn't the front trigger configured to fire the left barrel first, and have the more open choke in it?
I see no plausible explanation for it either way. I can shoot the rear trigger first and shift to the front just as easily as vice versa. Makes no diff to me. In fact, when shooting S x Ss at doves I very often do that, to take an incoming pair far out on the first bird, then take the second before it passes me. A true pair on incoming doves is very satisfying.
The only thing I would stipulate is that I would want all of mine were choked in the same manner, not the same constrictions in every gun, but having the more open barrel on the same side for all of them........whichever side that was on.
SRH