I think maybe by the time the end credits roll around it might be too late to be like "ah shit this movie wasn't brand new!" anyway, heh.
Wikipedia suggests opening credits were always incomplete credit-wise - "Films generally had opening credits only, which consisted of just major cast and crew, although sometimes the names of the cast and the characters they played would be shown at the end. " - but doesn't talk about copyright there. https://en.wikipedia.org/wiki/Closing_credits
It's a group of people that you pay as a Director and that sets the guidelines how work should be done.
https://starwars.fandom.com/wiki/George_Lucas#:~:text=The%20....
I don't have a specific recollection of if they included all the "legalese" sort of non-credits like these copyright notices.