Around a spherically symmetric source, the field strength depends only on radius, so every point at the same r feels the same pull. Direction points inward, but the magnitude is shared across the whole shell. This is the ideal central-field result; real sources are oblate and lumpy, and other bodies break the symmetry, while the radius itself is measured with ephemeris uncertainty.
Field magnitude depends on radius while direction points inward. Exact arithmetic here means exact results for the stated model inputs; measured inputs still carry uncertainty and significant-figure limits.
highlighted = computed this step
Equal radii give equal field magnitudes
Both bodies sit at radius 4, so both checked field magnitudes are 1.
gright=1gtop=1
Direction changes while magnitude stays radius-bound
The right body and top body use different inward arrows, but the value 1 is unchanged.