Well, the older you get, the less adaptive a brain gets. It's easier to learn a new language or adapt to modern technology at a younger age. As you get older, the brain becomes less of a sponge, and "closes off", more or less. It gets more difficult to come through. I think that's the thing here.
This also ties into the reactive tinnitus group being the most responsive. "The more reactive, the better", he said in the Q&A. In those cases, the brain is very much reacting to external impulses. It picks up on sounds, reacts to them, changes accordingly. So it would be more likely to respond to a treatment.
I'm not able to see these videos, but Neuromod also showing less glowing reviews, actually makes the positive ones more believable. Obviously these are not staged, as was speculated about before. They are willing to show nuance, and a more real responds. It's not all, BUY THIS WE GUARANTEE IT WORKS. Also, we KNOW there's a group of 20% non-responders. This isn't new information! All we know is they are willing to paint a more nuanced picture!
Man, negativity is read into everything they put out, and people are quick to make irrational assumptions based on nothing.