How is a tiny screen overlaid in an accessible field of vision, not totally obscuring your perception of reality, NOT "augmenting reality"? I agree it barely meets the threshold, but I don't write it off as not AR full stop.
By way of a real-world example, military pilots have heads-up displays that overlay IDs of aircraft on the aircraft as they appear to the pilot. That's AR.
My volvo has a heads-up display that show me my speed, the current speed limit, warnings, lane guidance... But none of that points to anything in my field of vision. Not AR.
Mercedes also have heads-up displays, and while I don't own one, I saw a demonstration where when you are using adaptive cruise control, it highlights the car it is following. That's AR.
The above is my lay understanding. If you buy this distinction between "heads up display" as a general term, and "AR" as a specific use of a heads up display, then Glass was not AR. It was just a heads-up display.
You don’t see reality and the screen at the same time. It is reality or the screen. (Just like a phone that isn’t running an AR app)
Looking at the screen does obscure your perception of reality because your eye has to change focus. The little prism was transparent but it may as well have been translucent because you couldn’t focus on the screen and the world at the same time.
But it wasn’t even mostly always in view… when you weren’t focused on it I guess it could kinda flash and make you focus on it, but it had no overlay ability.