> you can't generally guarantee that they are (even approximately) stationary with respect to each other...
False.
> ... because points on the earth's surface (in general) are not stationary with respect to each other in an inertial frame of reference.
True. There is both the earth's rotation, and the relativistic difference due to differing elevations. But given earth's angular velocity and gravitational gradient, points on the surface are still approximately stationary with respect to each other, where "approximately" is defined by the amount of difference it will make compared to the time precision that Google cares about.
False.
> ... because points on the earth's surface (in general) are not stationary with respect to each other in an inertial frame of reference.
True. There is both the earth's rotation, and the relativistic difference due to differing elevations. But given earth's angular velocity and gravitational gradient, points on the surface are still approximately stationary with respect to each other, where "approximately" is defined by the amount of difference it will make compared to the time precision that Google cares about.