Maximum demonstrated does mean just that - it's the greatest crosswind seen during certification and found acceptable.
It may be the actual safe limit, or the safe limit may be double that but they didn't get there in flight test. The only real absolute about that limit is that nobody should plan to exceed it unless they know the type extremely well.
And I for one have flown stationary or backwards several times in FW aeroplanes (and no, it wasn't a Harrier). Quite entertaining, but bad for the soul too close to the ground and can make navigation fiddly.
G