I wonder if it can just be explained by user error? Do we /know/ these tweets were actually ever on twitter? Perhaps the tweet about united failed to post. (It's happened to me). And if that happens to a few people who posted about United, you then get a conspiracy. But if the same thing happens to the cat picture you tweeted, it's chalked up to a bug and forgotten.
Though given Twitter's recent track record with "ghost-deleting" and "shadow-banning", this sort of thing - if true - wouldn't be surprising.