The point made is still valid since the EEC was created in 1957 and, before it, the Coal and Steel Community in 1951. Of course it is also unclear what they had in mind with that phrasing, and perhaps it even varied depending on whom you asked: The UK government under Thatcher signed it but I think we can all agree that she wasn't aiming for a federal EU (her famous "No, no, no" speech in 1990 makes it beyond doubt). I think the people at large did not want nation states to disappear within a federal EU, either (and probably still don't).