Why are RGB tertiary colors so similar to RGB primary colors? I was suprised to learn that RGB tertiary colors are much more similar to RGB primary then secondary colors.
I was expecting they will be halfway between them and look more like this: 


Rather then this: 


Is there a reason/purpose for this disproportion? 
(I know how to calculate values- this is not my question. I'd like to know why correctly calculated tertiary RGB colors seems to be much closer to primary then secondary RGB colors)
Likely a gamma correction issue. Tertiary colours are some permutation of (1, 0.5, 0) in RGB, right? So the issue arises because without applying gamma, 0.5 appears less than half as bright as 1, so the blended colour skews towards the primary (1,0,0) rather than the secondary (1,1,0). The image below has linear colour on top, gamma corrected on the bottom, you can see the gamma corrected colours appear much closer to a halfway tone.