The original thread is about AirPods (non-Pro). There was a conspiracy theory (that's the best word I can think of but may not be the correct one) a year or two ago because a bunch of updates to Bose, Apple, and other noise canceling headphones seemed to make the noise canceling worse and the rumored reason was they internally might have found hearing damage. AFAIK there's no direct or scientifically vetted information that this was the reason for the change.

Headphones and earbuds can cause hearing problems for quite a few unrelated reasons. People tend to increase the volume with headphones (I check the average audio level in Apple Health. I keep the volume quite a bit lower when using the Pro vs the original). Earbuds can compact earwax inside the ear causing pain, tinnitus, or hearing problems for some people.