Lol, the Jesuits were into politics up to their neck, the colony was originally under the diocese of Rouen in Normandie, Msgnr de Laval was first sent here in 1659 as bishop de Petrée, his nomination was subject to lots of politics, and he finally got named as bishop of Québec, which covered all of North America outside the English and Spanish colonies.
From the various records I have seen over the years, the use of Latin rather than French seems to have been an individual choice of the priests writing those records. As late as the 1670s there are some in Latin, Sillery records for example are like that.
The French king issued edicts in France obliging priests to keep records of BMD. A bit later, he required them to get them copied to central registries. Simple reason being that single copy is more easily lost. The biggest reason for these edicts was that the church was the only place where BMD records were routinely kept, and when there was a question of succession for example, they were needed. Not aware that the edicts specified a language for them, but I haven't looked at the edicts themselves.