I suppose that, in theory, he could have given away non-voting shares to some of his employees over time. But then I would have expected the press release to specify that he was the sole voting shareholder, rather than "the sole shareholder."

I don't really know much about the movie business, but my understanding is that new companies are incorporated for each individual movie project. The investors (of cash, franchise IP, or time) receive shares in that movie's corporation. Presumably the profits are then paid out as dividends, or the company is dissolved, and assets are distributed. That would explain why George Lucas never suffered any dilution on Lucasfilm, which presumably is just a shell whose main purpose is ownership of the various franchises and holding shares in the various sub-companies.

The whole shebang is owned by GWL. I once heard George say that he had no interest in going public. He wanted his companies to work on his projects before anything else, which cause a lot of grief at ILM some years ago.