While I ascribe to what is written in the pdf that Hermione linked to concerning horizons and pyramids in general, I'm not sure if it is fully applicable to the Great Pyramid due to it's radically different internal layout.

I'm also rather groping in the dark looking for something that we may be missing. My starting point for questioning some of what we see is not the sarcophagus, but by leaping forward over a thousand years and considering the various "Enigmatic Books of the Netherworld". This looks an odd place to start, but I believe there is a connection to OK religious beliefs. I'm not going into a ramble with unformed ideas, but I'll point out that while "Atenism" could be said to be the culmination of the 18th Dynasty move to a religion more tied to the OK solar cult than was previously the case, this is not the real culmination. Isn't it odd that we find on the shrines of Tutankhamun the first full account of the "Destruction of Mankind" in the "Book of the Heavenly Cow", but most intriguingly, the first "Enigmatic Book of the Netherworld". This cannot have just emerged from nothing in the little over a decade since the death of Akhenaten, and must have been as the result of long and deep thought over many decade, and I believe informed by what they knew of OK solar beliefs. There is no pyramid in those texts, but I do wonder if the "heart" of the GP, and a meaning lost to us, exists within those texts.

Well, a bit of a ramble, but it's a subject surrounded by swirling clouds of mist