Heated could mean that there is a heating pad on the outside bottom of the tank. Heated basement or heated underbelly are different.
RV Holding Tank Heating Pads | ModMyRV
Enclosed tanks could mean that the tanks themselves are each surrounded by a material of some kind. Usually, the entire underbelly of the unit is covered with coraplast.
There isn't much standard practice in the RV manuf. world. There are a lot of common terms that generally describe a feature that is usually fitted to the unit in a common way.
You'll notice that almost all RV manuf's. have the good old "specifications subject to change without notice" clause.
One can inspect b4 acceptance and accept or refuse the unit as it was delivered.