I use this green slime, putty stuff to clean out dust and hard to clean trapped particles on my phone and laptop. I forgot the name of it, but it's really useful. You apply it to your phone and pull it off. It collects any trapped particles.
Kinda surprising, since they're so small. But it did happen.
(Also, that's my next band name.)
It's because the holes are flush whereas most other phones the earpiece is recessed or even has some type of molding or accent that keeps the earpiece from coming into direct contact with your ear. This along with the aesthetics is a big reason I don't like this design of the One series.
I'm actually going to the doctor tuesday because I've got something in MY earhole. Very disconcerting. Sounds are distorted and it feels like I'm wearing an earplug. Sucks...
I kid you not, my sister knew a guy who was having a similar issue, but also kept hearing little squeaky noises in his ears. Went on long enough that he finally got it checked out. Doctor put some oil in his ear and --brace yourself-- a large spider slid out.