I’m going to provide the counter opinion here: I prefer CSD. SSD gives you a consistent title bar across applications, but it can cause a wildly inconsistent look within a single app. Part of the application is being themed by a different piece of software that doesn’t know anything about it.
I also like apps being able to make use of some of the extra space in the titlebar if they want to.
I’m going to assume this is Meta’s usual level of negligent greed, and there’s a decent chance that no human was involved. YouTube actually did something very similar.