We might as well declare the issue of break-in as a matter of faith. And as with all matters of faith, it's pointless to say I am right and you are wrong. Until there is direct, repeatable, and irrefutable scientific evidence pointing one way or the other, I'm not going to form an opinion.
After all, whether it's your brain or the speaker breaking in, the end-result is the same: you perceive the speaker's sound as improving. And since everything you can possibly experience in the world is subject to perception, perception is all that matters.
I can explain it to you but I can't understand it for you.