I've puzzled over this myself. I belive that both of your questions are true. I have a photocopy of the actual marriage record of Albert Perrot and Marie Louise Letourneau at St. Charles sur Richeieu. Here her parents are listed as Joseph Letourneau & Marie Angelique Denoyelle, of this parish. I do plan to eventually clear up this question beyond any doubt by getting copies of all the actual records needed to do this.
In the early volumes from the Drouin Institue, I found Louis Letourneau, son of Jacques Letourneau & Angelique Guyon, married Angelique Desmarets-Desnoyers, daughter of Jean Desmarets-Desnoyers & Therese Menard at Longueuil on Nov. 23, 1739. I haven't yet, but do plan to get copies of this record and related records (including Angeliques baptism) from Longueuil as well as any Letourneau records from St. Charles during this same time period. I like to look up the actual records because I've found that these kind of discrepancies aren't that uncommon.
I don't get up to Montreal very often, so I find it more cost effective (and productive) to photocopy any records I might need and sort it all out later. When I get home, I can take my time to properly figure it all out without being pressed for time. On my next trip, I plan to make arangements to have specific microfilms sent to my local library, via inter-library loan. This will help me do the bulk of the photocopying locally and use my precious time in Montreal to browse through indexes and look up marriage contracts and other notorie documents. I should have this figured out by spring. I hope!:-)
You might also want to check with Dot Drake about this. She has a recent post on this forum. She has done a great deal of research on Albert Perrot and Marie Louise Letourneau. I don't think I've specifically asked her about this myself.
My connection to this line is through the Bushways of Grand Isle, Vermont. ALL the Bushways from there are descendants of Theodule Bourgeois (AKA John Bushway) and Florence Perrotte, the grand-daughter of Albert Perrot and Marie Louise Letourneau