Hi - late reply to this thread.
Speaking as a GB umpire (and without binding any other umpires), the (S) (and (F) and (I)) grading are ruled as applying to rear contact, although when this issue was raised and everyone was looking at the precise wording I can see that a strict interpretation of the wording is that it does not apply if there are enemy in contact with rear and edge but not front.
Speaking as member of the Stavka group involved in the development of v.2, I remember a discussion with Phil about this. It was pointed out to him that the v.1 wording didn't seem to apply any grading factors where elements were attacked in the rear. He deliberately changed the wording in order that gradings should apply when attacked from the rear (it is only reasonable that (S) troops should be more resilient than lesser mortals in these circumstances). The exception for being attacked in rear and side is, I am sure, an unfortunate mistake in the wording.
Tim Child