You asked for evidence and I gave you some.
You cannot dismiss it so easily !

The size of the complex was chosen to be symbolic - the outside walls of the complex do this more logically than the inside.

Whatever was built before, this was the size that was chosen (1040 x 530 cubits), and there is likely symbolism in the final round numbers

Curiously, looking at the east wall in Lauer's diagram he shows 64 "redans" or columns and two end bastions, giving a total of 66 columns that make up the wall.

These are split by the entrance in the ratio 63 to 3 redans which is 3 and 1/7 times 21

If you take the half of the rectangle made by the walls we would have dimensions 520 x 530 amd the perimeter of this would be 2100. This is 100 times the 21 factor !

(fyi the half way line would correspond with the original mastabe north face)

Please do not try to propose that the walls lengths were not symbolically chosen.

Graham Chase