Yes, they do indeed say....

" Side-by-side barrels are better than over & under barrels because they have a broader and more quickly-acquired sighting plane."

Interestingly though they also claim...

" O/U or Over and Under [barrels] - Over and under barrels are better than side-by-side barrels because they have a narrower sighting plane."

Bit of a turn around but in fairness I think in both cases they are really talking shotguns, (field in the case of the SxS and clay target in the case of O/U) rather than Double Rifles meant for use on Dangerous Game.