It's clear north egyptians are whiter because they are closer geographically to other meds and mesos, but jumping straight from med-tan to black is exaggerated.
I think you are putting the more brownish south egyptians / Kushites / Nubians in the same bag as the black skinned ethiopian / sudanese cushite peoples.
The origins of Egyptians you refer to would, at best, exist between the historic kush kingdom and the persian border depicted here (remember, egypt was bigger like in >>3091269
Using "ethiopian" as origin is not acurrate because modern ethiopians were only tangentially related to nubians / kush, and in fact had their own kingdoms known for sea trade.>There is no physical barrier to seperate Egyptians racially.
there isn't a natural barrier to separate continental europeans racially either, yet you can clearly distinguish italians from frenchs, inberians, germans and slavs.