Well, JonS mentioned earlier that when in their "visible surrender" state, there is a limited amount of time for them to be recovered by being in close proximity to their own side again, after which they disappear from the map, just like routed units do now in CMSF.
I would also suggest that, while not realistic, having them appear with their hands up is a useful game mechanic to indicate their state and doesn't stretch realism too far given they disappear.