Well the thing is I am dual CN with blue and green and while training for CN I liked practicing on white more and so there is an imbalance where my white/yellow is 1 second slower than my blue/green but my orange/red is 3 seconds slower than my blue/green. Being dual CN it is easier to become quadCN because you are used to doing opposite colors so even if I practice white cross all day my yellow improves just as much. to become full CN would require twice the amount of effort because not only do i have to get 1 second faster on white/yellow but also 3 seconds faster on orange/red. It's much easier for me to pick up 1 new set of colors to adjust to for the short term and once I become comfortable with quad CN I could decide if I want to go full CN but I won't just switch to CN right away and it could be that 4 choices out of 6 could be enough to take advantage of most of the easier starts to solves.
Also the time it would take to surpass my normal average with Quad CN is faster than if I went full CN. Another thing that is nice is you most likely get extremely close to the benefits of full CN with quad cn. Whereas with dual CN you miss opportunities with 4/6 colors limiting yourself to 2 each time. quad CN lets you take advantage of the best cross most of the time and the chance of the easiest cross being on the 2 colors you didn't adjust to would be a minority instead of the majority like it is with dual CN.
My filter for white/yellow cross is really good compared to orange/red. I still insert into the wrong slot with orange/red but with white/yellow I can see an edge and know instantly where it goes.
So to summarize it is easier to be quad cn than being fully neutral because to be fully neutral you have to adjust to two different opposite color schemes instead of one, decreasing the work required by half.
I'm guessing that white pieces are just easier to filter period. There's a reason that most solvers that aren't neutral solve white cross. When I started with the beginners method, I was color neutral, but when I started F2L, the white pieces stood out, so I decided to solve white only. (This was before I'd read anything on how useful being color neutral is) I've since reconsidered that and started solving yellow also. At one point, I realized that I'd solved yellow almost exclusively for a while, and had to restore my white filter because I'd actually gotten faster on yellow than on white. I caught that before it became a problem, and now, I don't have any bias between white and yellow in terms of solving times or recognition. And I'm completely happy with only having 2 cross colors. But anyway, the point I was getting to is that white, and maybe yellow, are just easier to recognize. It would explain the disproportionate number of white cross solvers as well as why you're doing better with white/yellow than with orange/red.
It'll be interesting to hear how quad CN goes! It's fairly untested, as far as I know. I should probably explain better my doubts about it, although what you said does make a lot of sense.
My (completely unsupported) theory for why solving 4 colors might not be a good choice is based on the fact that the benefit you can get from having more crosses to choose from would likely increase at a fairly steady rate. The benefit you would get from solving 2 cross colors instead of 1 would be greater than the benefit from solving 6 cross colors instead of 5, sure, but not
that much greater. The cross move count would increase at a fairly steady rate, although the growth would accelerate some. But the color filter number is a different story. (I'm only going to mention the E layer because cross and LL are pretty easy to be color neutral with. It's F2L that's difficult) For Bi-CN, you have one E layer color filter. For quad-CN, you have 2. For full CN, you have 3. But the growth rate in difficulty of that is not even close to as constant. I would theorize that the difference in difficulty between having one (Bi-CN) and two (quad) color filters is greater than the difference between 2 and 3(full CN). The difficult thing seems like it might be having more than one, instead of a steady increase in difficulty as color filters are added. In summary, the relationship of difficulty of recognition and ease of cross solutions will be worse at quad-CN than it will at Bi-CN or full CN.
It is a theory. Nothing more. And you have more experience with neutrality than me, so I'm sure you would know better. But... opinion?