I wonder how much of that is really true. there are unity games that show much complex physic than this, which has custom movement for orbital mechanic and uses

I wonder how much of that is really true. there are unity games that show much complex physic than this, which has custom movement for orbital mechanic and uses physics mostly as a glorified stacking problem within connected rocket parts of which there aren't that many really. I guess most of the physic slowdown is some improvised custom code around joints that makes the solver choke