My If you look at the PNP trackers, you will see that they are issuing PR for people who submit their applications around Oct 2018. I have two guesses:
1- Any application before that was sent to detailed security check. Unfortunately, This security check seems to take up to 6 months.
2- It seems that the detailed security check starts after 11 months the application is received.
These are just guesses based on statistics and there is no solid proof for that.
By the way, I am in the same boat with you