Could this actually be a strategy from them to decrease processing times? If proof of residency documentation is now included with all applications, theoretically RO would not need to be verified independently by IRCC through CBSA or CRA ..it would be left to the processing officer's discretion to check in case they feel the applicant does not in fact meet RO despite the documentation... otherwise with most other straight forward applications it could make things faster?? Who knows....just my guess
My interpretation - guess only - is that it is to decrease processing times, but from a more simple perspective - they looked at the number of files where they had to ask for additional information (akin to the proof they're asking for here) and hence resulted in big delays (screwing their numbers up), and some related measures (the number of files - let's call them border-line - where having such information / evidence would have made processing somewhat/much faster), and decided that it would indeed make sense.
The trade-off - apart from annoyance to IRCC - is having more documents to handle and evaluate, but that gets less burdensome (physically at least) when they're being submitted electronically.
In other words: I doubt it's a big change in policy or a big crackdown, they just re-evaluated after moving to more electronic and some studies about where the gaps and delays occur. It's probably a net positive for the vast majority of applciants, for whom showing a few basic things like employment letters will make it more obvious they reside iun Canada.
For some subset it will be worse though. Mostly those who aren't living or working in Canada. Some individuals who are in Canada but live 'in the dark' or off the map or whatever you want to call it. Probably individuals working unofficially will face some issues.
But overall we will just have to see how ircc treats this. For most applicants with enough time in Canada, and a buffer, they probably won't need much at all. Ircc officers might ignore this info if the days in Canada is obvious and clear. So it will have to be based on judgment of the applicant, whether their case is easy or not. Applicants hate this.
And there's a possibility ircc will decide some time in future they got way too much info and documents, it takes too much time to evaluate, and doesn't add much value to their decision making and they end up cancelling. There's no perfect system.