Alternate universe?
not necessarily. And obviously not in name.
But once Jobs returned, Mac OS didn't stick around long, it was replaced by OS X.
Looking closer at OS X, and all the API's, commands, the netinfo directory service. No other Unix, or Unix clone used those, those are all NeXT items.
Also, think back to Apple Computers, inc at that time and compare it to today. Its easy for us now, to think of Apple as an electronics company with a wide variety of services in 2015, with iPads, iPods, iPhones, music services, etc. Computers are just one, of many things that Apple does now, and Computers aren't the big thing. I believe, that currently, the iPhone is.
Jump back to when Jobs, and NeXT were pulled back into that fold. All that stuff that wasn't there, and what stuff there was, (Newton, game system) were either failures or considered by Jobs to be failures.
That my opinion, and we all know what those are worth, but, from my perspective, Jobs and NeXT came in, took over, and saved Apple. All the other goodies were years down the road.