According to the linked documentation, Figma is opt-in AI features for all plans, and AI training on all plans except for Organization/Enterprise. Regardless of whether people have indicated interest in such features or not.
Also according to their documentation, all the AI features are in limited beta (hence the wait-list I mentioned earlier).
It isn't clear to me on re-reading the documentation if everyone is opted into training the AI, rather than just those who have opted into using the AI features while they are in beta.