...we still have a slew of 5th/6th Dynasty pyramids that share the same "T" configuration at the center of their tower core, the latter of which is also possibly very reminiscent of what AR and ZeA would have initially looked like completed. Coincidence or connection?
I'm not one for coincidences.
Every pyramid, however built, has a connection of sorts. Why particular dead personages wished to be interred in such structures provides endless debate on this board. However, for some reason or other, not all pharaohs were of the pyramid mindset - Shepsekaf for example. Therefore, pyramid construction was not a universal style of architecture for the dearly departed of the more illustrious ilk.
As has been discussed on this board as well, is the fact that, although pyramids may look similar externally, their construction is not based upon a standard model. It may have been opportunistic for the builders to take advantage of certain types of pre existing terrain or edifices with which to commence proceedings - the core of which you speak.
If this is correct - and there are numerous examples which can prove this to be the case - the theory of a pre conceived plan for pyramid construction which has a certain astronomical alignment, as proposed by Scott Creighton, Robert Bauval et al, should seriously be questioned. But that is the subject for another thread.
So - imagination goggles on - what would the landscape of Egypt look like prior to the construction of the core-constructed pyramids? Mounds, mastabas, hills, pits....
How likely is it that the architect/engineer/construction crew would prefer to build a pyramid miles away from materials - a logistical challenge - just because there was a pre existing core of whatever material at that site? Would it have been easier to build it from scratch with easier access to the necessaries?
As far as the leapfrogging of T shaped ground plans from ZeA and Abu Roash to Dynasties 5/6, again there is no evidence of a continuance of construction style as purported to have been, according to the experts. How did the Dynasty 5/6 builders even know what was under the layered pyramid built over the ZeA excavation?
In conclusion, there are similarities, there are connections, but there are enough anomalies (even at Giza) to provide sufficient grounds for further research on the subject of pyramid construction before anything definite can be asserted.
It may be worthwhile to group pyramids according to ground plan regardless of their suggested age or above-ground construction, as whatever is below must have come first, and ignore what may be, in many cases, a totally separate construction.
BTW. I've yet to be convinced that ZeA or Abu Roash were ever designed to be pyramids. In fact, the more I research, the more inclined I am to place them in a totally separate category.