Man I've been hovering this forum for a while and I've seen all cases!I think you get your oath invitation base on when your application was received not by when test was done.
It tends to be first-come-first-serve but it is not always the case, some things might delay:
- Different offices have different timelines... Scarbs seems to be one of the slowest! Meanwhile in Surrey BC seems to be one of the fastest.
- Amount of ppl on your application can delay, not necessarily, but usually if there's something wrong with one, the entire application gets delayed
- Too many international trips during your eligibility period can make it harder to confirm, specially if you drive to the US since they don't always stamp your PP.
I noticed they only put pressure to finish your process when you're close or over the 12 months periods.
This is just my observation, none of this information is official.