Ding,
Of course you are right.
The Alter Cup is about getting the best out of what is provided and that finds the best team.
I should have qualified my post.
"Had all the teams been equal" and they were allowed to vary their rig. The team that set their rig right for their weight would have been the quickest.
The added advantage of sailing your own boat at other regattas, in addition to setting up your rig you can also have sails cut to your weight. Although the rig is pretty tuneable.