Well, in that case, then Netflix's position becomes irrelevant; as they're drawing on something proven to be in the Public Domain, so copyright laws do not come into effect, due to having expired in that case.
But mentioning in a whole category shift "public domain" would be baseless and useless at best.
Though, come to think of it, a disclaimer would be useful as simple citation at that; for the simple case of finding out further data.