I've seen people with PPR have MyCIC say eligibility and background is in progress, and someone with an interview letter already yet MyCIC says interview is not needed.
I am convinced MyCIC is not updated and showing accurate info yet.
Even if it was, GCMS provides way more detail, and allows you to view the notes of the officer so you can see what they think about your relationship/application, you can see where your paper file is, you can see the dates something happens with your file.. It is something way more useful than MyCIC.