When they are processed in Canada, they are generally processed in order of arrival to their office; however, the interesting part starts when they are sent to out of Canada local visa offices, my assumption is that they throw the applications in a room where they gather dust for a few months (sometimes a year) and then a janitor opens accidentally the door and says "hey guys!!! there are some applications here, are you going to process them?".
As I have seen in GCMS notes, each stage has a maximum date to be completed, so if a visa office completes it one week (or even one day) before that date, they hit their monthly key performance indicator (KPI) and their processing is deemed a "success". It's no wonder the GCKey says that your application will move fast when its close to the end of the processing time, they only care about falling within those 20-24 months because then they can publish on their site that they processed 90% of the apps within that time
You are going to see many apps that were completed in 6 months (or even less), but they do these ones to average the system, so if you have 1 application processed in 6 months and another in 18, when you average, you have 12 months, which is considered very very good (compared to the standard time: 20 to 24 months)
I know it sounds crazy, but my application has been in "Application received" since it was sent to Mexico (August 20, 2019), so the theory might have some truth hehe