The wiki states this accepts an object or group, however when passing an Object (tested with soldier), the command appears to have no affect and unit continues its idle animations.

Adding 'group' before the object processes correctly, freezing it in place.

Working:
group <unit> enableDynamicSimulation true;

Not working:
<unit> enableDynamicSimulation true;

dynamicSimulationEnabled also appears to be affected in a similar way.