Improper conversion from CMYK to RGB or GRAY

Photoshop version 27.8.0.
I create test image ( 600 x 400 px 300 dpi CMYK 8 bit, no color management, 30 bit display unchecked). Fill it with (C100M0Y0K0). Entire surface is colored ok, each pixel is C100M0Y0K0, checked with magicwand and info panel and with conversion to gif, where i acutally noticed following:
When converting mode to RGB or GRAY, result produce pixels in two colors in a kind of diether/noise way. No any other function was used inbetween.
Converted RGB values for (C100M0Y0K0) are:
1. R0G173B239 - for which i think is proper conversion
2. R0G174B240 - this one i think shouldn’t be there and is probably generated by some function.
That two color pattern is not like “chess plate, there is no kind of symetry”, it is more like some qr code or as it  has been produced by noise function.

In short, two pixel of same value converted to another color system, shouldn’t convert same pixel value to two different ones.

Regards, 
Uroš Železnik