It gives you a ground that has instantaneous voltage variations from the ground on the other side of the choke.
I agree. A simple inductor in the positive side of the supply would make more sense.
I think it is a good idea to draw a schematic of your circuit and all its external connections, with each wire drawn as an inductor. Then try to visualize (or actually simulate) what external sources of noise and internal sources of current variation (like those produced by that switcher) will do to the voltage across those inductors. If the DC currents are significant, or the circuit has large DC sensitivities, include resistance in each connection, so you can think about where the DC drops will be, also.
Just throwing filter components or ground planes at a circuit without having a specific purpose for each (based on circuit analysis) is unlikely to provide anything like an optimal use of the available choices. Every resistive drop and inductive voltage needs to be accounted and compensated for or the compromise consciously chosen.