AS "The pyramid of Menkaure wasn't even imagined at the time Khafre chose his pyramid site. The two cannot be related in a reverse chronology."

This is your opinion rather than a statement of fact as you are presenting it.

If there was a plan then clearly it was imagined.
In the plan, The 2000c Giza diagonal was the design feature that linked them and the orientation of the line to north suggests the line was put in place after Khufu's and before Khafre's.

The fact that G2 axis is HALF WAY between G1 and G3 on this line (as Chris also describes) is what you would call 'a coincidence'. I find this opinion very unlikely too.

Graham Chase