You'll be able to know for sure, whether headphone burn-in is a placebo or not.

Hmm... none of my headphone plugs will fit down the barrel!

If you could actually fit something in there, you get your reward of a destroyed pair of headphones I assume. Or maybe it won’t sense a thermistor and nothing will happen. I’d assume without a thermistor it won’t actually function (although you could probably trick it)