I understand how this rule applies at a gate, but not at a downwind finsih. Rule 18.1 states "about to round or pass a mark on the same side". If a port boat comes into the finish line at the pin end, but your on starboard, the boats are not passing the mark on the same side.

In the preamble of rule 18, room is required if a tack or jybe is a normal part of manoeuvre. A jybe at the finish to me is not a normal manouvre.

What am I missing here?

Scott