> the term campsite conjures up a place with tents already there

You've never been camping. Ok.

I’ve been camping, on trips that ranged from “park on the side of the road and set up a tent” to “hike four days carrying everything” and also “drive to campsite, walk into permanent managed tent”. Sounds like you’ve only done a more limited range of camping trips.

I think you’re viewing this through your own cultural lens where camping can be totally solo (in the woods?)

In England, we can’t just pitch up a tent in the woods, we need to pay for a campsite where there’s other tents.

I suspect, from their description, this person is from a different country again, where camping may happen in large open steppe with lots of other yurts.