The ability of the French to form in two ranks had always been there, from the beginning. Even the died in creation Regulations before the one in 1791 had troops forming in two ranks as the norm. The French National Guard was always formed in two ranks. The 1791 regulations included instructions for two rank formations.
The question of three or two ranks had been debated in the French army for decades.
The commanders on the ground had the option of forming in two ranks when it was thought necessary and did so during the wars right through the Battle of Waterloo. IIRC, the 85th formed in two ranks at some point.
Whatever Napoleon's reasons/justifications for ordering the entire army to deploy in two ranks, real or not, 2 ranks wasn't all that unheard of or so far out of the ordinary for the ground troops. Two ranks were used when it was seen as advantageous. This was true for all Napoleonic armies. The Prussians in the 1793-95 often fought in two ranks, as did the Austrians during the same period... often the third rank was syphoned off to be used as reserve or skirmishers.
2 rank formations were simply on of the tools in the formation tool box, to be used when needed. Napoleon decided it was needed in 1813.