YuryShpilev:
Although I cannot check out the rules in all the ama tournaments in Japan because of so many tournaments, it is said that 27 point rule is popular in many ama tournaments.

I believe the rules except for 24 point rule have been created in order to solve the problem that no time exist for re-match after Jishgi in ama tournaments.(In Japan, the number of participants in the major amature tournaments are often much larger and the preliminary tournament term is usually one day, not using 2 days of full weekends, which is different from most Western countries).