Campsite Claiming Etiquette

Typically public Adirondack tent sites are first come first served, I get that. But I’m just curious what is the common consensus on the etiquette of someone coming in on a Thursday to set up camp for the weekend, but then leaves & doesn’t come back until Saturday morning with several friends/family? :confused:

I have definitely arrived on a Thursday before to try & claim a choice campsite for a weekend gathering, but never ever have I left the site unoccupied for a night or two only to return a couple days later to spend the weekend.
Is this legal?
Thoughts?