I believe your theory is entirely correct! I feel like that. Even within the space of a single interaction, I become more or less autistic. For example, I had to attend training on Tuesday this week from 9:30 - 15:30, non-stop social interaction and "learning" i.e. training! I even had to spend lunchtime with the trainer and the people being trained. I had no respite. At the start, I'm such a snazzy socialiser. I know exactly what to say. I know what to do. By the end, I'm stupefied. I can't concentrate. The lights are too bright. I'm punching myself, tapping my foot, rubbing my eyes, praying for the ending to come. Honestly, all my energy had been depleted by that time, and then I am struggling to function for a few days because it took so much out of me.
So, yes, I agree with your theory. I build up my energy reserves in isolation. Then I expend all my energy reserves on social interaction. I'm a skilled performer for a few hours, then I'm crippled. It doesn't make any sense to anyone but ourselves. I think it is probably best if we try to work out how much energy we have to spend...