I do not know it is earlier or later. The control guy side Steve did meet Linus to adopt linux. Somehow the personality not fix. He moved to BSD. Linus is very opposite to the Mach philosophy. Hence it may go the non-Mach way. I do not think the Mach sounds like Steve level choice. But if he has a hand the simplicity is. And the choice of objective c is also amazing. Still using unix (or linux) is the choice.