Didn't even think of that, yes of course XLR and for that matter, 1/4" TS/TRS connectors were originally for switching phones at AT&T, before automated switching. Incidentally, you can also blow up quite a bit of stuff with them, depending on whether they are at consumer "line level", pro audio "line level", or even speaker level. We're definitely too comfortable with "if it fits, it works" (or at least isn't harmful".
There was a wild period in early transistor electronics where DC power adapters sometimes used 1/8" phone jacks - before the barrel-style DC plugs became common. Having 9V DC in a form that could be plugged into a microphone input always seemed like a pretty insane choice.
I'd like to mention my USB-stick-shaped audio recorder/player who's headphone jack (only uses built-in mic in any case, though iirc the headphone button skips to the next file) functions as the computer and charging connector.
The device was shipped with a cable (USB-A male) <> (TRRS 3.5mm aka 1/8") for this usage. It reports as mass storage.
