The structural engineer specified the foundations go 800-900mm deep into rock - based on the soil report. Unfortunately in a few places it's taken 1800mm to hit rock, and that's going to need some extra concrete and the concrete pump a couple of more times to get it done.
It's a bit of extra cost, but I think you only get one chance to get your foundations right.
We also had to tweak the driveway drainage and retaining wall a bit based on how things actually look on site vs the picture. See image.