Man, I don't get you.
All the applicants go through the screening. Proof:
https://www.cbsa-asfc.gc.ca/security-securite/screen-verific-eng.html
How did you know that you'd been under comprehensive SS for 8 months? The only way to know it is to order CBSA notes to find out the type of your screening and the date when it was intiated. Did you order them?
Generally, agents can see if a file is currently processed by CBSA and tell you that your security is in progress. I was told it three times as I mentioned before.
Speaking about your case - the fact that you pass one particular stage doesn't make your file go straight to the next stage automatically. It often happens that files can wait for review by an officer to be sent to background check for months. For example, one guy passed criminality more than half a year ago and waited with "criminality - passed, eligibility - not started, security - not started" status for 6 months. Then he passed eligibility during several days, then security in a couple of days, and - boom! - he gets PPR.
So the fact that everything but security was passed, and you got to wait for 8 months, doesnt' mean that IRCC/CBSA/CSIS perfofrmed comprehensive security screening on your file. It may simply mean that nobody took care of your case and nothing more.