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...My point was a^^^^^^^^^^^^^^^^^^^^^^^^^^^^
counterexample that hydroelectric utilites are in the business of selling
electric power (i.e. work) produced by the action of falling water which
is pushed downward by the earth's gravitational field (mostly usual
Newtonian gravity with a small negative contribution from the centrifugal
force field from the earth's rotation) that *exists* (locally) by virtue
of our choice of a frame in which the earth's surface is taken to be at^^^^^^^^^^^^^^^^^^^^^^^^
rest rather than using a freely falling frame.
Just because a force exists in a
given frame by virtue of the state of acceleration of that frame wrt a
freely falling frame is no reason to consider that force nonexistent,
nor to
claim that such a force can do no work in that frame. I will concede that a
Coriolis force does no work on a mass (just as a magnetic field does no work
on a charge),
but centrifugal forces, Newtonian gravitational forces, and
forces due to other translational accelerations of a frame's origin wrt a
freely falling frame certainly *can and do* do work in the frame in which
they appear. (BTW, neither forces nor work transform as scalars under
transformations among accelerated frames, but that is no reason to claim
their nonexistence in any frame in which they do not vanish.)