One would think so, but shouldn't the main the goal be: sail as low as you can and still fly a hull? I do think better sail trim would make the boat pictured faster, even at the angle they are sailing.

BTW, sometimes still pictures do not tell the whole story - he could be dumping the main in a puff (which is not exactly the right thing to do in spi sailing, either - dumping the traveller would be less expensive ).