As a general point for that those shocked/appalled/mystified/spitting feathers over the fact that Deadheading Crew might just have an contractural entitlement to "proper" seats it is worth bearing in mind a few points: that in many airlines deadheading happens on Long Haul and Ultra Long haul services....12-14 hours on a jumpseat, minimum rest downroute, then operate back.....nope, not going to work. ..As far Shorthaul goes(and even on occasions Longhaul) at times and on some types there might be no spare cabin jumpseats, they are occupied by the "working crew" and as far as the flight deck seat(s) goes if "checking" is going one flight deck is occupied ( and on some types there is only one flight deck jumpseat). In short without "blocking" or prebooking or in some way reserving passenger seats for deadheading crew the whole operation starts to become fragile. Whether the use of a jumpseat was a last ditch option in this case TBH we don't know.
So whilst perhaps not relevant in this case but as a general point if some are now expecting an announcement that all dead heading crew are to be sat on jumpseats just to satisfy public relations you are probably going to be disappointed.