Like almost everything in life, it's all about playing games.
Athletes are playing one game. If you know how to play the game, you can try to win it. It's difficult to know how to win the game, if there are no definite rules. So to athletes, it seems unfair if you have played the game to win, won, and don't get to claim the prize, because of the actions of a selection committee.
But to people on committees, it's a completely different game. The intermediate prize is getting on the committee, so you can have power and influence, the ultimate prize.
If the selection committee was required to automatically accept the people who had highest placement at Nationals, there would be no point to being on the committee.
Presumably they believe Ross Miner is less likely to do well in international competitions - i.e., that their primary purpose in being on the committee is to try to insure that U.S. athletes do as well as possible in international competitions, based criteria that include placement in US Nationals, but also on other factors up to their own best judgement. But if they aren't allowed to use their best judgement to make that happen, there is no point to being there.