I have no insider knowledge on this.
But first: it's pretty clear that adding the staff in Sydney both sped things up for those at the early stages, and seems to have mostly cleared out the enormous backlog (given that from roughly March to October, AOR1s were just trickling out). Yes, there are a few files that have not received AOR - but very few (and who knows with those, perhaps sent back or something else happened). But basically the backlog has been cleared.
Going forward: I don't know what they'll do going forward. But I think just saying only 20% is done in Sydney and everything else is overseas where the real problems and delays are (with implication that staff needs to be hired in those offices) - it makes the assumption that IRCC's systems are not going to change and are still working with paper files as if it were 1995 or something.
Clearly IRCC wants to move to more digitisation where the physical location of the paper file is much less important - witness sending a lot of files to Beijing for some type of processing. Perhaps Sydney will take on more of the early stage analysis, maybe they'll take on more than 'just scanning', maybe they'll come up with a 'fast' procedure for simple files and the like. Maybe they'll stop moving the physical files anywhere at all and this means Sydney has to be beefed up (staff and physical space for archiving). Maybe they'll change the scanning process to include much more information and analysis and more usable digital files - but I don't know. In a world where the physical process has become desktop and phsyical files are dealt with as little as possible, a lot becomes redundant. (I personally would guess they'll move to a mostly digital process for family sponsorship in 1-5 years, but that they've accepted it can't be all digital).
As it is now, I suspect that only two people really "consult" the physical file in any depth - Sydney when scanning and checking for completeness, and the examining officer. But then another five-to-ten fold people are touching it and physically moving it during the process (not very efficient but made sense when it really was mostly paper processes, i.e. ten to twenty-five years ago, and everyone involved had to look at the physical file).
So going forward: I expect we'll see lots of little changes that seem odd at first that may mean more stuff happening in Sydney. And that may or may not mean more stuff in remote offices, or more staff, but it won't be one-to-one where applicants are from (leaving aside that quite a lot of files are mostly processed in Canada even now). Because it just doesn't matter for a lot of cases where the staff are. (Some of the changes with notifications around AOR1 - SA, bio, medical - hint at this, they seem to have decided that these don't need to be all at once, they're moving from more serial processing to more being done in parallel)
The other point is that lots of steps are done by outsiders like security checks and IRCC has little control - so it doesn't mean all files will be magically quicker. Countries that have more security issues and fraud will still take longer.
Plus there are still backlogs and logjams in procedures - interviews being the most notable right now. The transition to doing remote/virtual interviews has not been smooth or scaleable, and they must have an enormous backlog of those.
