'And how exactly is it that you know that this is not "genuinely unavoidable circumstances"?
You're making assumptions!'

Yes, it was more of a generalisation, as we have no idea why this particular buyer left it until the last day to open a request.  As you say, there are indeed legitimate reasons why someone might keep an item for 30 days - and this buyer's reason may well have been genuine, rather than suspect.  Or they might be one of those naturally disorganised people who leave such things to the last minute... or just plain inconsiderate/unthinking etc.

Whatever the reason, no seller appreciates a return request opened on Day 30... 🙄

Perhaps the OP could let us know if they were satisfied with the reason given, despite the unfortunate experience with CS, and the understandable frustration of the situation, believing it was too late for a return.