Ugh!! I thought pin weight was calculated at 15 percent of gvw... I am way off!!! How can the salesman say it is tow-able with some 1/2 ton trucks???
Sorry. Those types of numbers are used to estimate. Trailers are usually 12-15 percent for tongue weight. Fivers are more like 20-25 percent. The fiver you're considering is nearly 23 percent dry. That number will increase as you load it as the biggest storage areas are up front. Keep in mind that dry weights can be misleading too. They don't include options, batteries, propane etc. Delivered weights can be several hundred pounds higher. I suspect you'll be closer to 11k loaded.
As for the 1/2 ton towable? Manufacturers only need to find one that can do it to say that. There is a stripped down f150 with around 3k payload. With only a driver onboard it is technically "doable". Stupid, but doable.