Interesting question, I always assumed it was because it has truck parking in the back. I found this page but it doesn't give any details. It does have a phone number and e-mail you can try.
That rest stop is in Smyrna. It is about 3 miles from my house and it is open 24 hours. There is a very large truck parking lot in the rear and open rest rooms. They also have a dump station there.
Gary
Delaware
2006 Chevrolet Silverado 2500HD Crew Cab Duramax
2006 Outback 30FRKS