JD had some early results of people ramming into objects (i.e stumps, rocks, abutments, etc. ) and bending that closing plate in the front, to the point that the plate was not holding the FEL tight enough that bumpy travel was allowing the FEL to come off. So the safety device (Clamp shown) was issued to all early customers (I was one) and then became standard part with the new FEL's.
I don't use it, but do put a 3/4" bolt through the front plate and the front weight bar. That keeps the plate from coming unlatched.. plus I don't ram into things to bend up that front plate.