Another issue is simply the load on the server running the calculations. While a hard border for gravity is less realistic, it is much easier for the system to calculate than a soft/gradual border.
Although, if we're talking realism, there's no reason mag boots wouldn't work on a moon. A planet, sure, but a moon is low gravity anyway, and we're talking about exos/robots, with literal ankles of steel.
Mag boots would work fine on pretty much any planetary body that's significantly smaller than Earth.
About the only thing that wouldn't work is jumping while upside down on a ceiling.