Yeah, I've looked at the document checklist, and it definitely tells you to skip all of that. It certainly looks as though CIC doesn't require it. I've looked over the country-specific guide, as well, and there's nothing in there, either, about your plan to return.
As we filed inland through Québec, not outland, I don't know about the outland process. Perhaps Québec asks for proof of your intent to return when you apply for the CSQ? Not sure. Hopefully someone more familiar with the outland process through Québec will be able to help. *If I were in your position, I would still probably provide some information on your plan to return. It may not be necessary, but it may save you some time down the line if they already have what they need, instead of having to request it from you. You already have to put together proof of your relationship. Personally, I would add information about my future plans to the proof of relationship documentation. After putting together a timeline document to discuss the development and continuation of the relationship, I would add in a bit like, "We plan to live together at x address in x country until pr applicant is granted pr. Then we will be returning to Québec together. We will initially reside with my parents at x address (see letter documenting their offer to let us stay with them) while we search for housing in x city. I have searched x website and see a lot of job opportunities in my field. My spouse plans to continue her education and has familiarized herself with admission requirements at x university, where she will apply after receiving PR," etc. Just discussing your basic plan to make a life in Québec, how you plan to find work and support yourselves, how you plan to deal with housing, where you will live, showing you're familiar with the province and have given real thought to what you will do when you return.
Out of curiosity, how long did you reside in Québec, and how long have you been living abroad?
*Notice, I say this is what I would do in your position. I am NOT an immigration consultant, nor am I an expert. All I know is what I learned through my own experiences, and what I've learned from the experiences others have shared on this forum.