As far as I am aware the term “Cognitive Impairment “ was coined by the defence team and had no legal definition. The AAIB report ruled out physical impairment like g LOC on the grounds that the pilot was making control inputs right up to impact. So the jury was presented with this argument.
The pilot was experienced and professional
This experienced and professional pilot did something really wrong.
The only explanation is that he was “cognitively impaired”
Which explains every mistake any of us have ever made.
If I was Mr Hill, I think I would leave it at that!