Edited for simplicity. I really would like an answer to this!
When I open a DNG file of an Xrite Color Checker in Profile Editor and use the Create Colour Table feature in the Chart tab, I get a colour chart with RGB values that bear no resemblance to anything I'm familiar with. e.g. The green patch of the Xrite in ACR reads 94, 148, 71, while in Profile Editor it reads 25, 48, 19!
If I open the file and don't use the Create Colour Table feature, but simply choose Apply Camera Raw Adjustments from the Options menu, the RGB readings from the colour patches still bear no resemblance to the ACR readings.
Secondly, if I highlight, say, the red patch in the colour table and reduce the luminance slider, the red patch in the image darkens (as it should do) but the RGB value remains the same!!