There actually is some curvature/dishing/something non-planar in the faces of the Great Pyramid, a lot bigger than 4 mm. It can be seen in the shadowing of an aerial photograph alleged to be from the 1940s:
but it took careful surveying to measure it.
Combined High Resolution Laser Scanning and Photogrammetrical Documentation of the
Pyramids at Giza:
The middle is farther away than the outer edges. I hope the color-coding is obvious.
Here Martin.au got hold of the raw laser data and posted some cross-sections:
There was a very long discussion of the GP and its measurements and their possible meaning at talkrational.org.. Since the casing is mostly gone it's difficult to take what we can measure and convert it to measurements of the GP as-built. Febble posted a very good summary of the problems with the older surveys that seemed to indicate some special meanings of the as-built measurements
here, although you might need to learn a lot of background to appreciate it fully.
Bottom line: the available evidence clearly and unambiguously indicates that there are no meaningful numbers (year length, polar radius, etc.) encoded in the GP.