That's irrelevant when discussing ownership. He owns 17% of Meta. That he retains control of 90% of Meta doesn't mean that he has the moral right to ignore his responsibilities to his co-owners.
No one has the moral right to do anything since the entire idea of moral rights is absurd. Yes, Zuckerberg has a duty to act in the best interest of shareholders. Courts have repeatedly ruled that good faith belief is all that requires. Unless you think his interest in button ui is somehow in self interest over company interest he didn’t do anything wrong.