so instead of chasing retreating squads it would be more logical to stay there?
That is a different story. For most units and in most situations it makes sense to chase squads.
But I was talking about how a soldier picks picks a model of the targeted squad. Nobody knows exactly how this is determined, but I am sure (this means I saw some values referring to this in the editor) that distance is a factor. So if another enemy soldier comes closer than the originally targeted one, this could cause a target switch.
I was always under the impression that this does not happen that frequently, but Sanders post read as if this was regularly the case, and he is way more experienced than I am.