[Publius6961]

Another reason for believing in these skills is their accurate calendar. The Egyptians could not have devised a calendar with such remarkable sophistication unless they were well-versed in astronomy, a science we cannot dissociate from either mathematics or religion in ancient Egypt. A nation capable of mastering astronomy must have possessed advanced mathematical know-how.

This is the opinion of someone who wishes, really badly, that the explanation be so.
Given enough time and dedication, an accurate calendar can be devised with no mathematics whatsoever; simply many observations over a sufficiently long time, using nothing but sighting poles.

Astronomy is still astronomy when based solely on observation and, yes, I can very easily disassociate work based on visual astronomy from mathematics.
The same holds true for the Aztecs, the Incas, and every other primitive culture which never developed real writing, so as to keep records, diaries, laws, inventories, and untimately, mathematics in the abstract.

[scrabblehack]

Also, wouldn't those shafts pointing to the stars of Orion's Belt be pointing there at a particular day and hour (and combinations thereof)?

Circle of diameter 9 = 63.61725124+ square units
Square of side 8 = 64 square units...0.6% off...not too bad..