Measuring a difference can show a difference exists, so it's a very important step. One I would love to see more often when someone makes claims of objective changes to a driver.
But audibility is a completely different matter. Only a controlled listening test can really demonstrate audibility. and that's where things get annoying:
-We don't have time travel at disposition so we can't have someone A/B the before and after headphone. We can record something at both moments and the listener will A/B that, but someone will argue that the headphone used to listen might mask the differences. Or that the recording isn't precise enough, and question the experiment that way. So if no listener can tell a difference, we're back to the usual argument that blind tests are set up for people to fail them. At least if some listeners pass, we can conclude that something does sound different and start to look for the possible cause/causes. Which in this context of he says, she says, would be of tremendous value.
I've tried that once and couldn't pass(TBH what I measured didn't suggest there was something to hear).
-Other option, we could use 2 pairs of the same headphone and only "burn-in" one. We'd have to first confirm that nobody could tell them apart at the beginning. Otherwise the test is meaningless. Except that having to switch between headphones takes time and is impractical to test, both before and after. You'd have to take the headphone away where the listener can't see and have randomly the same or the other headphone given back to him, hoping he can't tell from the heat remaining on the pads, shape of the pads, or something else. Each switch will introduce a few dB of variations here and there because of a slightly different position on the head(change in the trebles, perhaps in the low end due to lesser seal). most of all, 2 pairs of headphones rarely measure close enough to be completely indistinguishable, so not only do we have to procure 2 pairs of the same headphone, we might need way more than 2. This test is hard and can easily be contested and found inconclusive.
I haven't seen anybody even trying to do it properly so far. That one seems to be a bust.
We could just have someone try the headphone new, and then try it again after 200h of burn-in and ask what he thinks.
Here the listener will have to remember perfectly some event from at least 200h ago, when research suggests that we start altering our memory of a sound sometimes as soon as a handful of second after hearing it. Super reassuring! So if someone feels like something is different, maybe it is, maybe some slight change in how he focused caused him to memorize something else, maybe he's noticing the difference between the actual sound and the imperfections in his memory of it? we don't know.
Oh and whatever he will answer, we have no way to confirm if it's true or not!!! Because, wait for it, this is not a test at all. It's us asking for somebody's opinion about a memory. No control is in place to check if he's correct or not. Worthless in term of getting conclusive evidence of audibility.
Of course that's what everybody claiming to have heard driver burn-in, is relying on.
So while you argue that we can close the topic because some of us have excuses prepared to reject any evidence(some do seem to act like that), I'd argue that we're still waiting for some legit reasons to start it. right now I've seen more reasons to believe in dark energy or UFOs, than in any sort of benefit (objective or subjective) coming from burning-in our headphones. doesn't mean they don't exist, of course lacking evidence doesn't disprove something! but then again, maybe when I tell my headphone "I love you" every morning, the sound improves. do you want to discuss that possibility in 30 different topics where nobody has any legit evidence of anything but loves to claim to know stuff anyway? seems like a waste of everybody's time, but not for the reason you proposed.