The LR CC Soft Proof RGB values shown in the Histogram are incorrect when the cursor is hovered over a specific area of the image. It does not matter what color profile is used or if the ' Graphics Processor option is enabled or disabled in LR Preferences. The values remain the same and incorrect regardless of the Profile selected in the Soft Proofing panel.
The Soft Proof Histogram appears to display the LR Native Color Space values (Melissa RGB) without RGB data conversion to the Profile color space setting in the Soft Proof panel. Please see this post for further details: