Your guess is correct. If they fit your ears they stay in very well.
In fact they are so comfortable and so light, it feels like I'm jogging without earbuds at all. It's quite a dramatic improvement.
Good to know.
The second issue I have with these AirPods are - what is their life-span?
When their batteries eventually die, what is Apple's solution, other than the dumpster, for them?
Asking because this is a very Green company.