Several things you mentioned occur to me too -- and I have a pop up! Some private CG's do not allow POP UP'S for the same reason you mentioned. The
RV'ers think they look 'trashy' next to their Big Rigs. So I just move on down the road. Also the 3-night stay. Most private parks are going to this especially in the hot vacation spots. They have figured out that they will 'lose' a night's fee if they don't do this, and if you want to stay there you will pony up. If not, you can go on down the road, like y'all did.
My first thought is why didn't you want to stay at Garner SP? They allow tent camping and have hot water/showers?? I'm just curious.
Anyway, glad you eventually found a spot to enjoy and had a good time!