technically though, what does IP2 mean then? Why are there so many cases of applicants getting their PPR mail within 2-3 weeks of IP2?
This myth of IP, IP1, IP2 etc was started by some lost soul who thought that a specific update in MyCIC account correlates to a specific stage of the application, which unfortunately is false and unfounded. However, this myth caught on, and also because it was placed on the months threads as the opening post for quite a while.
Most applicants will see PPR after their BCK starts, but this is not the norm. For many, BGC may never change and still the PPR may arrive, and for other, it will change, and PPR will not arrive. Therefore it is just assumption.
Further, IP, IP2 etc. is no where present in the Immigration and Refugee Protection Act (IRPA), the law under which the applications are processed. IRPA and the regulations provide the following stages:
1. Completeness Check (R10, i.e. regulation 10 of the IRPA)
2. Medicals (See
https://www.getgcms.com/blog/medicals-preparation-expect-diagnosed-ailment-comprehensive-post/)
3. Criminality
4. Eligibility (A11.2) (See
https://www.canadavisa.com/canada-immigration-discussion-board/threads/march-2018-aor-join-here.546504/page-155#post-7032535)
The eligibility takes place in 2 stages. First an program assistant or analyst will review an application and then the recommendation is reviewed by an officer who makes a final determination. This stage is also the longest, barring any security or SS. This is the most crucial stage, and if this is passed, then your application is 90% through. Only after eligibility is passed, will the security commence.
5. Security (See
https://www.canadavisa.com/canada-immigration-discussion-board/threads/the-anatomy-of-a-background-check-in-depth-analysis.500146/)
To read more on stages, see
https://www.getgcms.com/blog/express-entry-application-processed/