Studio Ponoc had Miyazaki's blessing. I doubt the same can be said for OpenAI. OpenAI doing this without even asking might not be illegal, but it comes across like an act of incredible disrespect for the very creators that these memes are masquerading as an homage to.
“When we opened the new studio, Studio Ponoc, I went to report this to Mr. Miyazaki,” he went on, “and he gave his blessing and said, ‘You really need to have the conviction to go create a new film studio and the conviction to show children worthwhile films. And every film you make, you’ll have to realize that has to be a film that is worthy to show to children’.[1]
“When we opened the new studio, Studio Ponoc, I went to report this to Mr. Miyazaki,” he went on, “and he gave his blessing and said, ‘You really need to have the conviction to go create a new film studio and the conviction to show children worthwhile films. And every film you make, you’ll have to realize that has to be a film that is worthy to show to children’.[1]
[1]: https://www.themarysue.com/studio-ponoc-interview/