GIMP 2.6.5 and CMYK information

Dear dpreview members,

I have been reading these forums since few years. Thank you for all the valuable information and advices posted here.
Now its is finally time for my first question.

I am mostly a PSE user, but would like to be able to replace it whenever possible with GIMP. The version of GIMP I am using now is 2.6.5 (SuSE). I was pleasantly surprised (OK probably this was possible also before) to see that now the CMYK values can be displayed in the "Sample Points" window. The problem is that only three of the values are different than 0. The fourth is always 0%.

Example:C 0%, M 34%, Y 50%, B 49% must correspond to R 51%, G 34%, B 25%. I am aware that one can address the same color by different combinations in CMYK, but it seems that the default conversion of GIMP is ... strange.

Cheers
D.