[btilly]

I have no idea if there was a conscious choice either way. However the goal was certainly, "Our cooperative multi-tasking system where any bad application takes out the operating system no longer cuts it, migrate to a preemptive one." And building on Unix was the shortest path there.

There were many disconnects between the two systems. See https://www.usenix.org/legacy/event/usenix2000/invitedtalks/... for some of them.