I read this thinking about how movie studios tried to have a fully encrypted chain between the TV, the cable, the graphics card, all the way down so that HDCP would prevent anybody from putting something in the middle to record movies onto.

I don't think it's beyond the pale to argue that some shady headphone company could throw a cell modem into a set of over-the-ear headphones to exfiltrate audio. I just can't see the business case for it, even considering shadier business cases.