This is what I tend to believe (as a very high scoring introvert on various types of tests). Introversion in a physiological sense is high sensitivity to external stimulation. Fill up the bar too fast, it can cause an anxiety response.

Some people then struggle with dealing with overstimulation, leading to anxiety disorders and a learned aversion to high stimulation situations/environments which often social situations are.

The nuance, I think, is that what constitutes stimulation isn't objective and will vary from person to person.

I'm no psych, but this sounds more like a description of the autism spectrum than introversion.

It very much is not what autism is. At a superficial level you can describe some of the characteristics this way, but autism is vastly more complicated then a simple sensitivity to stimuli.

Like I said, I'm not a psych, but I was diagnosed with inattentive ADHD as a kid and had to get medical waivers approved to join the military and fly. Channelized attention and having to force myself to focus on mundane, boring tasks (with varying levels of success) are a thing I have dealt with my whole life. Oversensitivity to stimuli is not.