Yeah, Sydney has a lot of nested cities. They’re all admin level 9, which can be quite small.
It looks like this huge Sydney recently lost its admin level status in OSM. I don’t know if that really matters for our use here … I typically gravitate towards relations with some admin level value as a good indicator of cities in an area, though, so 
maybe that huge Sydney never deserved to be in CityStrides at all? I really don’t know.
There’s full coverage of New South Wales at admin level 6 (click the top left run button) which includes Council of the City of Sydney
There’s also full coverage at admin level 9 (those tiny places) which includes this tiny Sydney
This conversation has come up before & @liz attempted to help me understand, but it’s all a bit complicated … mainly around the fact that this massive Sydney exists - if it didn’t exist, I’d be able to add level 6 and go on about my day. 