Mmmm ...
Well your clue is with the manufacturer .... in their wisdom they have NOT allowed for both Hydraulic systems to be able to be turned off at the same time .... if there is a failure the 2nd system automatically becomes the active system .... what does that tell you?
BTW ... during my conversions on to both the Bo105 and the BK117 it was emphasised that the aircraft become uncontrollable with both systems U/S.
I don't think that has changed.