I think it's fine. Well, "validity" is contextually sensitive of course. For example, if I want to test addresses against a regex I'm developing then, yes, they are valid but if I want to test my mapping application that geocodes addresses then made up addresses are "invalid".

Since the whole point of an address is that it resolves to a particular geographical location then I would have expected a "Random Valid US Address" to be able to be geocoded.

The same can be said about credit card or social security numbers - that they should validate to actual cards/people, yet a generator would be expected to not do that, but only produce series that match validation criteria.