I won't detail the dealership, but I will warn EVERYONE who is going to purchase a travel trailer to demand an EXACT tongue weight before purchasing a camper. There is NO reason an RV dealership can't do this. If they say they don't have a tongue scale, run away, that is not a reputable response.
DO NOT BELIEVE the websites of the manufacturers. They specifically use a stripped un-optioned, empty , no propane, no battery trailer as their basis for their charts. The trailer manufacturer ABSOLUTELY KNOWS every single pound of every option and what it does to gross weight and tongue weight. It is a LIE if they claim it's not possible to know in advance. They design them and build them, they know precisely where the balance point is and the axle(s) and coupler, and if they add anything they know what weights will be.