I'm sure someone can give a better explanation, but from what I understand, countries were originally going to be given the chance to compete for extra qualifying spots through a series of all-around World Cup events (which were different from the World Cup events Jade competed in to earn her individual spot). However, those events had to be cancelled due to *********, so they went back to results from 2019 Worlds to grant countries the extra spots - in the women's division, the United States, Russia and China each got one extra spot for the Olympics. This spot is not attached to a specific gymnast (the way Jade's earned spot can only be used by Jade and no other American gymnast).
However, where I am confused is when people upthread were talking about the U.S. gymnasts essentially competing for two spots. I understand that one spot is 99.9999% guaranteed to Simone, but shouldn't there be three team spots after that? Is there another gymnast who people are currently seeing as a lock for the team?