For working adults sure. For students? Really? You expect students to do that? I think students apply for such a committee to learn how to do it and since they are still learning, it's not ideal to expect them to have plans for such things.Yeah that does make sense for Japan, just seems a bit overly rigid imo.
I disagree with this part though. With a competent management team, it's not difficult to keep a list of people who have requested a slot and to allocate slots to them based on cancellations - it's a negligible amount of extra work with a proper plan in place. I know this because I have done precisely that for work events with a few hundred people in attendance.
Still, even for students, if the cancellations and such are done in a proper manner, then it'd still be manageable. But a lot of the time the students that apply would do it either figuratively or literally at the last second. I had several students apply for cancellation and registration on events 2 days before the event started. Like, what the fuck people?