Second, you claim it shows a "provably weaker hippocampus". But the study doesn't show that at all. It shows less activity in the hippocampus, which would be entirely expected, much like if we offloaded translation to a computer, we wouldn't see the same level of activity in the language centers of the brain.
The researchers themselves only conclude this from their study:
> These results help shape models of how hippocampal and prefrontal regions support navigation, planning and future simulation.
That's it.
