Those are the weights provided by the manufacturer not actual as-built weights and usually represent the most stripped down model they offer. This is often done to assure that they will come under certain limits for towing as well as taxes in some states that tax trailers by weight/weight class. It also helps "suck in" unsuspecting buyers who what to tow with a smaller vehicle.
If you looked at the older ads for Scamp
and others you will see some weights that are near impossible in the real world.
But, all that said, I have soooo little interest in 30' stickys that I have already spent too much time talking about them.
Let me/us know if your interest returns to FGRV's and I/we can offer advice about what I/we know.
All I can say is Buyer Beware.....