macOS is designed for keyboard + mouse in mind. Not touch screen.
It is also designed for a certain sized of screen when paired with keyboard + mouse.
I've used 2007 netbooks with 5-11" screens running Windows XP. If the GUI is not designed for a certain size of screen it will
not be better at anything.
It is currently designed around mouse/keyboard, which does not mean it will never support touch. It is not designed for a minimum size screen, it's designed for a minimum resolution. Since you can change the scaling in MacOS, it could default to the appropriate scaling. People who buy ultraportables, not netbooks mind you, accept the compromises of a smaller screen.
Prior to 2006 Mac OS X only publicly ran PowerPC chips.
Publicly prior to 2020 it only ran Intel chips.
Once MacOS dropped PowerPC support, it didn't start again.
Seeming Mac chips are an outgrowth of iPhone chips then why couldn't it run macOS?
Even the A12 chips used in the AS Dev machines were custom designed to handle a desktop OS with extra components added for things like virtual swap memory.
Mac chips can run iPad & iPhone apps.
However, iPads can't run Mac apps. Developer support has been very limited because of the costs of testing and supporting a different OS without being able to charge for the effort.
What is being asked is the macOS GUI to appear when connected to a USB-C display.
And I said that I think requiring an external display is only beneficial for people who want to use MacOS in places where they are guaranteed a display which means no airplanes or trains, a few hotels, and a few corporate environments. Basically as far as MacOS is concerned, if you couldn't travel with just a Mac mini, you couldn't travel with just an iPad.