I did the CAD test at Gatwick, having failed the Ishihara during the Class 2. I also failed the CAD test, but I was quite tired, and others who have done it I think would agree that it is mentally quite draining. I'm not convinced that it is purely a reflection of colour perception ability.
As the videos suggested, I think the CAD test is still somewhat irrelevant. The CAA (like most other British institutions) take pride in implementing everything to the letter of the law, therefore if medical experts have concluded that the CAD test is an accurate reflection of a person's colour perception ability, and some other expert has concluded that a certain drop in colour perception ability is hazardous to flying, that will pretty much be the end of the debate.
I'm not sure common sense frequently comes into British decision-making.
As the content of the videos suggested, the important question is not, whether these tests provide an accurate diagnosis of a CVD, but whether or not a CVD will prevent you operating an aircraft anymore safely than someone without.
The problem for CASA, is that ICAO standards are largely based on those established by both the FAA and CAA, who have both adopted this test, or at least the FAA are planning to adopt it.
If they continue without adopting it, they probably perceive themselves as risking their credibility, which might be crap, but they will probably submit to international pressure.