Nice when that happens. A friend has one of those little chinooks (mini campers). All but one campground has accepted it as a "vehicle" and not a camper. At the one place that didn't, the camp host said "if you sleep in it, it's a camper" - so, if you had a minivan and slept in it, it would be disallowed as the "second vehicle".
I suspect part of the campground's decision in your case was because you did pay for the appropriate number of campsites - you just wanted some leeway as to the placement. Had you only paid for 2 campsites, they might not have allowed the TC as a "vehicle".