Yet another Introverts v Extroverts question

I'm watching Logan struggle with yet another introvert issue. It's sort of a big deal. Not necessarily RIGHT NOW, a few weeks before his 8th birthday, but it could be a reason people view him as rude or weird or fill in the negative adjective in the future. Pointless greetings.

I would imagine for many introverts (myself included) pointless greetings are as painful and useless as small talk. They make absolutely no sense and we'd prefer to just ignore them. However, we're adults so we say "Good morning!" multiple times each day to the same people we see daily an in the exact same context daily. But hey! Why am "I" rude for NOT saying good morning but the extrovert is "polite" for saying good morning and possibly making small talk and ripping me out of my deep thoughts? Am I being selfish for not wanting to be bothered for something pointless or are they being selfish for needing to talk constantly?

Logan isn't shy. He's not particularly outgoing, but he's not afraid to talk to teachers or other adults. He makes friends at the park and loves participating in games and group activities. He orders his own food at restaurants and will happily answer any question the waitress asks. That is, UNTIL we get one of those overly chatty waitresses who tries to engage him in small talk. At that point he stops talking and will no longer look at her. But I don't think he's being bashful as much as he just doesn't understand why she's asking such silly and pointless things and is confused about coming up with an instantaneous answer. I imagine one part of his brain is shutting down in panic, unable to come up with an answer while another part is wondering if this adult is perhaps mentally challenged for asking something so pointless in the first place? Obviously, I relate.

Our issue right now is Logan's latchkey teacher saying "Good morning, Logan!" and "Have a good night, Logan!" Logan NEVER responds. I don't think he's being intentionally rude, I think he can't make sense of the exchange. I mean, if he happened to run into this same teacher at Target, it would make sense to say hi because it would be acknowledgement of an unexpected meeting. The whole "good morning" day after day after day baffles him.

I don't know how to approach this. The rebellious part of me wants my son to stand up against stupid social conventions. The sensible part of me knows rebellion will backfire and every extrovert he encounters will judge him as rude or stuck-up. How do you explain that even though something makes absolutely no sense you HAVE to do it because it's the socially acceptable way? WHY is it the socially acceptable way? Why is it polite? Why is it required for him to follow what the extrovert needs but completely unnecessary for the extrovert to follow or understand in any way what he needs? Freaking extroverts! :)