I've never seen this problem you're reporting. The pixels are, in all of the screens I've seen and in every version of the software I've used, the same four values. The brightness doesn't change depending on the info mode.

Is it just that there's fewer "lit" pixels in that mode, so the overall amount of light emitted is less? You know, like the difference in overall brightness between watching the movie and watching its credits?

If you are sure that the actual display brightness is really changing, check here.