Here is a small picture to illustrate the problem.
While technically the intermediate colors are not actually in RGB, they are definitely picked from the non-linear transitions between control points.
We are taught by native gradients to have blatant straight transitions between colors and don’t expect these to happen with other hues.

The image on top is what we have now. Why yellow becomes more orange the further it goes form the point? Why green becomes darker and deeper? What is the color in the bottom left corner and where it comes from?

Sometimes we need only those colors we defined and their intermediate values.
Take a look at the bottom image — I faked it manually. This is what we expect to get out of these three colors.
I think a second mode should be introduced to allow this.

This is a massive issue! I am trying to make a gradient between a 25% grey and a 100% black. Solid colours of both are under the shape with the gradient applied and it is quite obvious that the gradient doesn't match the solid colours. This needs a fix ASAP! I pay a monthly subscription for working software, I don't want to just wait until someone gets round to fixing these bugs.

I run MacOS 10.14.5 and Illustrator 23.0.4

It seems like if the gradient doesn't extend exactly to the object's boundary that either a lighter or darker colour extends beyond the gradient.

If you make a freeform gradient with 2 points - 1 a light colour and the other dark - and ensure the points remain within the middle area of the object you'll see that the colour that extends to the edges doesn't match either colour from the gradient.

Windows 10 running Illustrator 23.0.1.

Created 2 colour swatches - light blue and dark blue.
Applied a freeform gradient using the 2 swatch colours.
Created a solid fill object underneath with the light blue swatch.
The freeform gradient's light blue doesn't match the solid light blue; the gradient is lighter.

Hi Egor,

Thanks for reporting this issue, Illustrator team really appreciate this.
We are not able to reproduce this issue “Freeform gradient shows RGB values when you work in CMYK space” , Kindly provide us some test file/video/gif so that we can investigate this further.

Thanks
Ankit Goyal
Illustrator Team