Do most state parks have a 30-foot length limit?

When we first took our 38 ft. motorhome into a national park (
smokey mountains) I filled out the registration and put down 38 ft. the clerk changed my 38 to 32 and said with a smile 32 is our limit and said my site was plenty big and this week I was 32ft. Had no problems and was impressed with a federal employee doing that.