When Jobs announced the iPhone in 2007 he said it was running OSX but what that actually means is anybody's guess. iOS is closer to macOS in functionality today than the iPhone's first OS.

I personally liked iOS and macOS being separate things because making a desktop OS also work on a touchscreen has wider implications than it sounds. That's why these days everything in Windows is blown up like Fisher Price software and way bigger than necessary for a mouse cursor. Seems like that's the direction Apple is headed in anyway with Tahoe.

What he meant was that it was running the non-user touching parts of OS X. It was possible to SSH to an original iPhone and install gcc and compile applications. It was sort of like OS X in a kiosk mode.