As pointed out, a thicker board or more copper doesn't necessarily mean better in this application but it is a lot more road worthy. The small bump in cost allows for a better board that performs and looks a lot better than a thinner one.
They had to do something more than just include a premium set of tubes to help differentiate the Heritage model from the standard CL. A better board is also a good marketing feature.
Well, that was my point, the boards are NOT thicker, there isn't a big change, if ANY change. EVERY maker of Ampeg has used boards at least that thick, if not thicker......
Which is not to say that the amp isn't pretty nice........
But that hype is a little like saying "our automobiles have a superior type design using 4 wheels"........
)