I would hate to say that but see this way that there would be tons of new files to be looked upon. But don't you lose hope when I lost all hopes to relocate to Canada that very instance I got the visa. So have you done the biometrics and medical?
There can't be a fixed reason, the backlog had done a lot of damage. Moreover this 6 July thing is big news these days. Don't work mine also took a while like roughly an year to get.
But it says work and not study anywhere, research more I am not sure international students get this shorter period of study. Are you an American citizen?
Did you previous work permit expired? Usually the SIN has a expiry date but you can extend it by showing the new docs like new work permit. If it starts with 9, yes it expires with your work permit satus.