Your eardrums are effected by the difference in pressure between the inside and outside of your ears. The absolute depth has no relation to the force on your eardrums. For someone with previous perforations, it may be easier for the eardrum to perforate again, but this would be because of infrequent or forceful equalizations. It could happen in 10 ft of water. Anybody's eardum would burst if unequalized at 25 ft of water.
Even if you had identified yourself as an ENT Specialist MD, In order to even half believe you I would require links to published studies verifying nearly every absolute statement you have made here.
The most knowledgeable ear doc I've spoken to is not an ear doc; just a GP at a Haleiwa clinic. He sees serious watermen and women on a regular basis, including many famous big wave surfers, and is an experienced waterman in his own right.
The most common North Shore Oahu ear perforations are from water "slapping" the ear drum, at the surface, not at depth. It is likely that people who have had more than one "slapping" perforation have a hammer (malleus) that is positioned &/or shaped in a way that predispositions them to easier slapping perforations.
When I cliff dive higher than 40 feet, I prefer to have a wax plug in my right ear. I have never had an issue with my left ear. It is likely the slap has something to do with the positioning of my right hand and head when entering the water, but my hammer position is also likely problematic.
Frequent swimmer's ear infections can also cause weakness to the ear drum, but mostly from the wrong self treatment. Over drying with rubbing alcohol and overuse of hydrogen peroxide for ear wax removal and sanitation do not make the ear drum all it can be.
If we look at bone breakage, I believe the data shows that a healed fracture is less likely to break again than the adjacent never broken before bone. I would like to see data on ear drum scar tissue strength vs non scarred adjacent ear drum tissue strength.
IMHO, I think it highly likely that more than just a few people often go to at least 25 foot deep pressure, very quickly, without equalizing their ears and do not rupture. It is surely painful, as the pressure of the water pushes the ear drum against the hammer, but I find it pretty unlikely that everyone's ear drum would burst, or there would be way more perforations being treated at the clicic in Haleiwa.
