The facts are the facts. Some ½ tons can be equipped tow in excess of 10,000 lbs. My 2011 F-150 is rated for 9500 lbs. towing.
However if you figure about a 1200 lbs. tongue weight and a 200 lbs. driver you are probably near the max cargo capacity. You can probably squeeze in a bit more if you do not mind the wear and tear of a couple of hundred lbs. over the max cargo capacity. Anyone who has worked a farm during harvest has seen that.
All the max towing rating from the manufacturer tells you, is that the some specific models of trucks are indeed designed to tow that amount of weight without damage to the vehicle. They make no claims as to what else the owner intend to do with it.
From the RV dealer’s perspective, such advertisement is a good selling point, because the dealer can say in all honesty that with “a properly equipped TV” you can tow this rig with a ½ ton.
In the end it is up to the BUYER to know if he has the TV to match the load. If you tell the RV dealer you have a ½ ton TV, he will assume it will pull the load, just like the dozens of other ½ tons owners he has sold TTs too.