That's because the US was not part of the Berne Convention until 1989, so before that U.S. works often had protection only if certain formalities were met (like registration or notice).

Wow. I didn't know that. Looks like this is a very US thing. I looked up now and TIL that US adopted the Berne convention as late as 1989. I'm surprised. So this movie released in 1966 didn't have default "all rights reserved" due to Berne convention. But most European countries, like 80%, had adopted the Berne convention by 1925. So when software was developed in Europe they automatically got "all rights reserved".

They aren't the same thing. Under US law pre-1989, publication without notice would lead to a loss of copyright, but publication WITH a copyright notice, that is, publication of a copyrighted item, meant all rights were reserved (unless licensed).

Copyright is a right held over the ownership of a piece of IP. A license is a permission slip that allows you to exercise actions that would otherwise be reserved by copyright. There is no requirement for a license. It's not a state of a piece of IP.

I believe that was a forgotten renewal of copyright status.