Additionally, I would like to add to your autistic analysis of the situation here with some of my own 'sperging by saying:
The hayes command set was developed specifically as a standard mechanism to dial and configure modems which didn't use external handsets or couplers to operate. That was the whole point of hayes commands. Even through the 80s before the hayes command set was standard, most modems of the day did not use a coupler. Couplers fell out of use long before that because they topped out at pretty low speeds which would have been close to useless for downloading anything substantial even in the 90s. They were also mostly designed to fit the standard Bell / Western Electric style handsets -- which by the 90s were already rare. John is probably confusing his life with the popular 1983 film War Games, where the young computer savvy bad-boy Matthew Broderick uses a modem with an acoustic coupler to infuriate Dabney Coleman and nearly start WW3. I think this tale is much like John's memory of "going to Space Camp" and being "shuttle commander" which -- according to John's timeline -- coincidentally happened roughly around the time of the 1986 movie "Space Camp". In the movie a group of kids, including a young Joaquin Phoenix, go to Space Camp where one of them becomes shuttle commander during a mishap where they are accidentally sent into space.
John likes to spout off about all of this anachronistic trivia and make it out to be some kind of computer wizardry, but this is shit that pretty much any nerdy middle school kid with a computer did back in the day. So, while I'm sure John probably fucked with modems and BBSs and shit back then, his telling of the tale is, shall we say, highly stylized.