Whoa whoa whoa there.
Read the rule below carefully. At the start they were overlapped. There is no proper course before the start. Therefore the leeward boat can luff as high as she wants before or after the start. But of course has to give the windward boat room and time to react. I'd have to hear the protest in order to asertain if room and time was given.
17 ON THE SAME TACK; PROPER COURSE
17.1 If a boat clear astern becomes overlapped within two of her hull lengths to leeward of a boat on the same tack, she shall not sail above her proper course while they remain overlapped within that distance, unless in doing so she promptly sails astern of the other boat. This rule does not apply if the overlap begins while the windward boat is required by rule 13 to keep clear.
17.2 Except on a beat to windward, while a boat is less than two of her hull lengths from a leeward boat or a boat clear astern steering a course to leeward of her, she shall not sail below her proper course unless she gybes.
Mike Hill
www.stlouiscats.com