prism, as doug stated, the velocity valves are part of the leveling system that some manufacturers chose not to install because of cost. it is offered to all, but it is not up to hwh to dictate what parts a manufacturer chooses to use or not. just as we cannot dictate which leveling system any of them use.
any part added to a coach cost money, nothing is free. most mid line and high line coaches have these valves.
note, i said most, not all.
doug may have misread the op post, but hes still right about the velocity valves.