Some of these arguments have been done to death now, and just aren’t very relevant unless you’re talking in theory rather than the reality of a location, like here.
The geometry of the liens for a cross platform transfer would have made the whole system slower. It works well in some cases, but it isn’t really appropriate for what was trying to be achieved here. Sydney’s also at the stage where it’s trying to get some diversivication in mass transit arrival locations in the CBD. I’m sure we’ll see future metro stops for a say a ‘beaches’ north south line do some parallel transfers.
There was a lot of time spent on the comparability issue too. The reality is that you don’t need the whole network to be compatible. And the places that do push this always have their own sub-optimal rolling stock for various situations. The airport connection metro vs the suburban commuter metro is a classic example, like it will be here in Sydney. The western lines are bigger heavier rolling stock with fewer stops to go faster - as they should. It’s never going to be a great result using a suburban metro for that. London’s Heathrow express is not the same as the Piccadilly line is not the same as the Cross Rail…etc etc. just because it’s called ‘Metro’ doesn’t mean the intention is for them to be the same thing. The benefits of compatibility are pretty scattered and niche when you’re looking at the scale of a large city metro system, and often seem to be simply because certain people like a ‘tidiness’ in decision making.