I don't know if it's true that Bluesky users also use Twitter. I know it's not true for me.

I'm also not sure why anyone would be angry if FFXIV joined Bluesky. They are already on multiple social media networks.

Even if what you say is true and it's lose/lose wouldn't it make sense then to join Bluesky because they would potentially be reaching more people?

Also the people doing social media are not the ones fixing the game, so I don't think that's a concern.