Survive !== having a lot of money. UBI assures that all people are "survivable" w/o any effort. Therefore, there is no competition to survive in any case. Hence the contradiction.
For a system which targets killing off "unfit" people, what would be signs of killing off too many people? Killing off too few?
Instead of a stack-ranking system, is there some minimum bar that they imagine people should have to exceed? I wonder how many people would have exceeded that bar 500 years ago, or 500 years from now.