Regardless of whether iPadOS has distinguished itself from iOS by a little or by a lot, what I was trying to point out is that the comparison doesn’t bring any value to the discussion. Because it operates under the assumption that everyone thinks that’s a bad thing, that iOS has a deeper form of insufficiency, unrelated to screen size. But again, for some people, all they want is iOS but made for a big screen. So iPadOS is perfectly capable for them. So saying iPadOS is incapable just because it’s iOS made for a big screen doesn’t make sense to them, because that’s exactly what they wanted. The only people for whom that argument makes sense are people who already find iPadOS insufficient. The only way to make others see why you need iPadOS to be more is to simply say what features it lacks that you need.
Yes, you said macOS isn’t designed for touch, that’s why I said a touch version of macOS, ie. designed for touch. That would mean completely redesigned with large touch targets, gestures, etc. It would have to look and operate very differently from how macOS does now, but it would have all the same ultimate capabilities. I’m not sure if you mean you want just some select Mac-like functions on the iPad or all of them, but if all of them, then that’s what I mean by a touch version of macOS.
Not sure if I totally followed your multitasking idea, but I agree there is room for improvement for Stage Manager, and in many areas of iPadOS.