It may all have to do with CIC wanting to determine how driven the Canadian citizen is to go back to Canada. In some cases very little may suffice in some others more would be necessary. A well established relationship may infact need less proof. Of course, this is all especulation on my part. We are a relatively new couple, together for 22 months and been married for 13 months. While waiting for part of the documents that were requested from my spouse, I actually went for a job interview in Canada and received a job offer. The documentation request included a statement quoting regulation 130(1) alone (seemingly to suggest that I could not sponsor the application because I am living abroad when in fact, sponsorship was approved months ago). We assumed the request was incomplete and was missing the part where they requested proof of my intent to return to Canada. We sent a package this week with the documents that were requested and included a quote for regulation 130(2), a copy of my birth certificate and passport ID page, plus proof of recent visit to Canada for job interview and actual job offer letter, housing research done and which rental places we have narrowed our choices, moving truck reservation (as I will star work there on June 1st), Canadian Bank accounts recently opened, etc. Short of moving to Canada already, I am not sure what else would constitute proof of my intent.
