This. Unlike other countries, Japan doesn't use body of work to determine who will be on the team. One exception being for an injured skater who has an extremely strong body of work like a gold medal at the Olympics or Worlds in the previous year. JSF will go with the top 3 women at Nationals.
About Mai and Kaori, I don't really think they were underscored. I think Daria was overscored in the LP at SA, but Kaori dug her own grave by popping her flip in the SP and messing up her final spin in the LP without those errors she would have been ahead of both Young and Daria.
Mai was probably underscored ( compared to others) in her SP at SC but I thought she had a few ignored URs in the LP so the final score was correct. I don't know why Mai got the benefit of the doubt in the LP when most other skaters didn't but it compensated for her low marks in the SP.
Wakaba's PCS should have been higher in both programs imho. However, the technical calls made against her were correct and she hurt herself by popping her 3Lz and as a result having 2 fewer triples in her FS.
Some people here like to hate on Rika but she scored over 230 points at both of her GPs in the 2019-2020 season the last time she was on the GP. Has any other Japanese woman ever done this? She just doesn't have technical issues for the judges to call except for an occasional UR. Hope she gets healthy soon.