Finally watched it. It is a good documentary but I've been told by someone who has no reason to lie that there is a bit that's not mentioned in the interview which arguably justifies why GL was upset. I don't think GL cares now.
Personally, I think Prowse isn't invited to Celebration anymore due to more recent issues such as his FB bitterness towards LFL and not being able to let go of some issues.
Fair point, I'm really only basing my opinion off this documentary which may not be fair on George, who lets face it, is a great man, not only for giving us star wars, but also for donating the money that he sold lucasfilm for to charity!