In the context of work experience, I think assessment means assessment of work experience, and because we have confirmed that Sydney does not do this, then it has to be what's done by Ottawa officer.
I posted this before, but on my CAIPS notes, Ottawa officer made a note that begins by the following, just before he made a request for POF and PCC from me
In this context, assessment means going through the application against the selection criteria (number of points), so I think it's safe to assume that between 'application and assessment' should mean between the time you submit your application, and the time your file gets opened by visa officer, not by the CIO.