Just glanced at your diagram. I like it. A coincidence of lines may have arisen from the following. Take a circle with a diameter of 280 royal cubits, and calculate the area using pi = 22/7. This is the area of a triangle with a base of 440 and a height of 280 as in the triangular vertical section of Great Pyramid on north-south axis in royal cubits. Now divide the area of the circle into 2 semi-circles. Now divide the the triangular vertical section of the Great Pyramid into two halves. A horizontal line at 82 royal cubits is symbolic of dividing the Pyramid's Equal Area Circle into two semi-circles. It follows that the area at a level of 82 royal cubits is half the area of the base, from which you can then see why your lines coincide; it does not necesssarily mean that AE was interested in this aspect.
I mention this because just a few moments ago I made another entry on the shape of the Bent Pyramid and its symbolism in digits - and showed that the Coffer in the Great Pyramid can be related to a circle with a diameter of 280 royal cubits through a symbolic dimension in digits. Therefore the Coffer, and the floor on which it was placed, can both be related to a circle with a diameter of 280 royal cubits.
It may be that the Pyramid's Equal Area Circle was symbolic of the sun, and that the division into semi-circles somehow translated the king into a union with the sun in ancient belief.