A vehicle you're buying either has a Salvage Title or doesn't have a Salvage Title so yes the car dealership always has to disclose clearly to the buyer whether the car has a salvage title or not.
If the dealer does not disclose the vehicle as having a salvage title then they may be in trouble if you take them to court after getting a salvage title when it wasn't disclosed.
If the car dealership is honest then they'll disclose the salvage title to the buyer if it has one.