-OT, but related - for the same reason, offshore vessels set their autopilot targets say, half a mile off the oil rig/whatever they are headed for - just in case someone doesn't pay attention as they approach.
I once saw a nice enamelled sign on a bridge stating 'Whoever programs a target on target will be promoted to figurehead prior to arrival at said target.'
(And, in that position, being the first to regret their sloppiness. Plus, they will somewhat soften the impact. Cough.)
If an engine relight doesn't happen, they won't hit the barge.
I think the biggest danger to the barge is a final engine relight without enough fuel, or with a guidance and nav systems failure or error.