Lots of people have such green lines on their phones

Samsung phones are really bad at this especially. Particularly newer ones

From 14 to 31 is still pretty rare. (I checked, population is ~6mil).

And at such a low rate relative to the population, if you’re assuming most cases don’t report it, the difference in reporting could pretty easily be increased awareness that reporting it was an option or some other similar cause unrelated to an actual increased failure rate.