True, the rules pretty much say they can pick whoever they want. It doesn't matter how many of the criteria you have, as long as you meet one you can be picked. But in practice they usually go with the top three. Remember 2 years ago, Higuchi had the most qualifications, but they took Sakamoto because she did better at Nats.
They never said why they chose Sakamoto. That was obviously part of the decision-making process, but we have no way of knowing to what extent.
And Sakamoto did have other qualifications besides Nationals placement. Anyone other than Kihira, Miyahara, or Sakamoto won't have that claim to make...which is why I said that, realistically, their only chance to make the team is to win Nationals outright.