Yeah, it seems short, but considering they didn't have to do that at all, it's still a nice gesture on their part. The short period could be due to the fact that, if that BTC20 is unclaimed, they'd have to divide it among participating miners according to their share at that time. And as miners' come and go and could change their pay-out addresses, redistribution of earnings after a longer period of time could be difficult.
I wonder if F2Pool stated how exactly is the unlucky sender supposed to make a claim. I wouldn't be surprised if they got flooded with spam messages from either jokers or scammers pretending to be the sender, so it might take some time to weed out the fake ones and verify the real one.