PLUS there were multiple versions of each of those.
There were actually rumors and concerns that, moving forward, Apple would do the same with the NeXT stuff. Because they did do the same with the NeXT stuff.
For a year, Apple had Mac OS 9 (Classic) and Mac OS X Server (which was based on NeXTStep).
Amazingly, saying, "We're just gonna ship one thing to everyone, and change the features depending on the distribution" was actually novel.
That same basic strategy persists today, since macOS, iOS, iPadOS and tvOS are all ostensibly the same operating system with different interfaces.
That seems a stretch, MacOS, iOS, iPadOS, tvOS seems like the Windows ME, Windows 2000 problem but 100 times worse.
For instance my mother searches for a covid tracking/checkin app on the iPad app store because she only has an iPad and it isn't even there despite running fine on iOS, it's just the developer is expected to put in the extra work to specifically support iPads so they never bother.
Maybe there is some secret option somewhere to show iPhone apps but she certainly can't find it, or even begin to understand why my Dads iPhone can have the app but not her iPad.
That an application doesn't support iPadOS, but does support iOS is a developer choice, and has nothing to do with the underlying operating system.
Anyway:
> First, we’re going to have a single OS strategy at Apple. We’re not going to have a dual or a triple or a quadruple OS strategy like some others. We’re going to have one OS, and that’s very important to us.
And twenty years later, Apple still doesn't have a single OS.