In a manual-approval-only group I was a part of in the past, we had a problem where we would decline peoples’ join requests and they would almost immediately re-pend back into the group. This was pretty bad for group management as not only did we have to screen people wanting to join our group, but we had to review join requests of people we already declined the day before. You might have recognized someone you declined earlier and could decline their join request without having to review their account a second time, but we had multiple people reviewing join requests so personA might have declined personZ’s join request the day before, and personB doesn’t know this and reviews personZ’s account again and then declines them. This can continue on where almost every person in the group that could manage join requests had reviewed any particular person’s join request, and it’s not just one user that we had to deal with – we had a ton of people doing this.
If someone’s request to join a group is declined, they should not be able to immediately reapply to join the group. That doesn’t make sense under any pretense. Group leaders should be able to set a timeout period (in days) before someone can reapply to join the group to make managing join requests manageable. Ranks in the group with the appropriate permissions should also be able to lift the timeout period on a certain person’s account in case their join request was accidentally declined (e.g. in a “Decline all above” spree).
Edit: It would be best if the group page still said “Application Pending” instead of “Declined. Please wait x days.” so people didn’t try to reapply on different accounts.