If the behavior is occasional, that's not introversion or "barely introverted".

E.g., if an extroverted-outgoing girl who is the cheerleader & prom queen & organizer of the 10-year high school renunion needs a few hours of alone time in her bedroom to cry because her boyfriend broke up with her, that does not mean the cheerleader is "barely introverted". She's also not 1% introverted and 99% extroverted. Sure, all humans need some alone time for various situations. But that's not what introversion _is_.

And just because I attend social functions and smile and laugh with friends for a few hours doesn't mean I'm "somewhat extroverted". My baseline is introversion and even if I do activities that outwardly appear like extroversion, that does not change the baseline of my underlying tendencies. I have been playing the lower bass notes of the piano with my left hand for decades but that doesn't change my underlying right-handedness. My right hand is still the dominant hand.