The reason is that Tint and Color are YCbCr controls.
Anything described in R,G,B doesn't need a color decoder because Magenta is just R+B, Yellow is R+G and Cyan is B+G. Those tint shades are already calculated for the display because it's described in the displays native colors. When you move to YCC, everything is described relative to RGB primaries via a color matrix, in order to convert the YCC data into the correct RGB levels you have to have advance knowledge of what that matrix should be for the content.
This is where the rec.601 v rec.709 thing comes in, when converting the RGB data into YCC data it uses the primary RGB data to build the matrix to try and maximize the useable YCC codes.
Just for reference:
Red RGB: 255,0,0
Red YCrCb:54, 256, 99
Green RGB: 0,255,0
Green YCrCb: 182,12,30
Blue RGB: 0,0,255,0
Blue YCrCb: 18,116,256
White RGB: 255,255,255
White YCrCb: 255,128,128
So you can see the R + G+ B = white.
This is actually the same for YCC as well, the Y's add up to 255, when you look at the Cb,Cr data it's actually +- data centered on 128 (A Cb value of 99 is actually a -29). When you account for that, the Cb and Cr values both actually total 128, 128. The part where you can see how the rec.709 standard comes in is that Y is the luminance information, Red is 21%, Green is 71% and Blue is 8% of the Y, because those are the exact Y values for rec.709. And those Y values are derived from the x,y chromaticity of the Primaries that add up to D65.
But matrix and the match to convert that YCbCr data into R,G,B data that the monitor understands. So the tint and color control tweak the standard matrix to either exaggerate or minimize the CbCr difference to decrease color luminance, or twist the CbCr values so that the output is more Red or Green or Blue.
Even know if a something does process RGB to apply tint or color, they first convert it into YCC then back to RGB.
Regardless, you don't need color and tint anyway. RGB data is already correct, and if your YCC decoder is funky your color and tint controls won't fix it. More often YCC decoders work correctly in movie mode, so they are also correct at default.
Bottom line, calibrate to rec.709 and don't worry about it.
CalMAN Lead Developer