... maybe he lapsed back into pedantic schoolteacher mode in his agitation.
I missed those first few ep's where that was established about him (pedantic teracher), but as changed as he has seemed lately, it's the change a young guy imagines about himself after some big, new more adult life experience. You have an image about what being fully mature is, then you have that new experience, and you step into that role you assume you're supposed to be assuming, based on that experience, and you're very glad to have "matured". Then something comes along to shatter the "role", something humbling, you return to what you always were, and you think, what happened?
Then the actual maturing starts, in dealing with that... or it doesn't.
I think Tim's supposed to be a bit younger than Don B seems to be.