You sound pretty introverted, but it doesn't explain all behaviors, which is my intent. To do so, you have to also explain why sometimes I am introverted by your description, even for years at a time, and then at other times I am extroverted, with similar time scales.
> If the behavior is occasional, that's not introversion or "barely introverted".
I mean to say it's between occasional (extroversion), and constant (introversion). This means there's a certain probability of it happening, so you're right, it could be rarely, occasional, sometimes, most of the time, almost all of the time, and all of the time.
So I don't disagree with you, you can make a clear demarcation, but then the words are much more useless. And if you're close to either side then you might as well call yourself an introvert or an extrovert.