I think at this point it has become clear that these confirmations are being issued at the discretion of the officer and their availability to work on issuing the documents. Any interpretation of order or pattern in their workflows is probably just based on the sequence in which the applications appear on their screens. Later applicants who receive confirmations earlier than others are probably just lucky tearaways passed on to other case workers with free time.
This was pretty much what happened when I was at the Montréal airport. There were barely any case workers, whoever was around worked at their own pace and didn't really care about the amount of people waiting. When the crowd got too big, they asked people to stand in line outside (this was after hours of waiting). Students were rounded up and handed mass-printed permits.
My wife and dad were visiting me for the first time (dad on a visitor visa, wife on SOWP). I was also returning with them and had a valid work permit and visa. We had to wait in line for 5 hours because no visa officer was available to examine/interview everyone (there were over 50 people in the line). After a long wait, we were taken from the queue to another section of the airport and told to sit down for another hour. Then, at random, an office staff member (who obviously wasn't an immigration officer) took everyone's landing documents and passports, sat down in front of his computer, printed everyone's work/study permits, and handed them out like movie tickets. No document verifications, no checks, no questions, nothing.
This was pretty much what happened when I was at the Montréal airport. There were barely any case workers, whoever was around worked at their own pace and didn't really care about the amount of people waiting. When the crowd got too big, they asked people to stand in line outside (this was after hours of waiting). Students were rounded up and handed mass-printed permits.
