I have pulled up a short distance from someone clearly packing to leave and waited for their site on occasions. My wife may have even sat at their table. I've also helped someone pack so I could get their site.
But I would never park in front of them. Nor "Hassle" them about leaving time at least not till, Well at the two parks I stay at check out is NOON so long about 1pm I might get upset if I was waiting for a site.
Last time where I'm parked I told someone what site I was vacating as I packed up this computer and headed back to check out. he pulled ON site as I left.
But again. No hassle, he did help me pick up my leveling planks.