What if you then had a HYD issue
think about that for a second... the horn is going off already, do you think a hyd failure with the horn already going would have been noticed by, um, the horn maybe pinging inbetween the baaping??? The little red light on the dash would be the only warning besides the lock up after acc depletion...... so no, turning the horn off wouldn't have made a difference.
He had also set up an auto of around 60kts so wouldn't have made much difference to a Hyd failure.