these methods don’t account for all the variables that reality has. People across all boarding groups will be late, there will be people that need assistance from flight attendants, there will be people who want to switch seats to be near their family, there will be people who can’t sit in the exit row, there will be people who need to use the rest room, there will be people who’ve never been on a plane before.
There is no great, full proof way to handle it because people are unpredictable