Your Turns 70½ column seems to have errors, but they don't affect the RBD. Should be
Jan 1949, July 2019, 2019, April 1, 2020
June 1949, December 2019, 2019, April 1, 2020
Also, I think that someone born on July 1, 1949 reached age 70½ on December 31, 2019, making their RBD April 1, 2020. That half-year thing made for an ugly calculation. I use 183 days for a half-year. Much better that it's now based on full years, although there still might be a question about someone born on January 1. Do they reach the RMD age on December 31 or on the following January 1? On what day one "attain" a particular age, their birthday or the day before? I think for Social Security purposes it's the day before, but I don't know if the IRS does the same.
You are correct that nobody had an RBD of April 1, 2021 or April 1, 2024 except those who were using the still-working exception with respect to a qualified retirement plan, left service from the corresponding employer in 2020 or 2023 and otherwise would have already had to have started RMDs from the plan.
