SRM is correct on his explanation. As an windward overtaking boat, you have to assume that the leeward boat is going to defend his position by luffing you up - it is clearly within his rights as long as he gives you room and opportunity to avoid contact. It happens quite often in both mono and multi fleets.

Your best defense as an overtaking boat is to set up for the pass in advance and try to climb over the leeward boat with 2+ boatlengths of separation. This way the leeward boat will usually not act as aggressively as you overtake, and it will give you room to head down after you've broken the overlap.