I too am suspicious of the chronology, and just as suspicious of what evidence the find contains for the description of the inhabitants as comprising a “very advanced civilization”.
The stone works do not appear very advanced if compared to some ancient locations found in different places around the world - where massive (multi-ton) stones have been placed together in exacting precision, constructing massive edifices.
And the ankh symbol itself has been found around the world.
That is not strange when you acknowledge many same symbols have been found to have been in use in different civilizations, which can just as easily suggest something common in human thinking and perception (how we translate ideas to images) as opposed to a universal prior common civilization.
Was glancing at an experiment’s prototype the other day, which had cavities bearing a striking resemblance to an Ankh in three dimensions. Perhaps an Ankh has no relationship to any religious symbology, but is a legacy representation of something that has become distorted myth.