I believe you might be referring to what happened in 2019? [1] This is a separate issue. [2]
I do clarify this in the blog post, although it might be better to move the relevant text near the introduction rather then in the middle of the post.
EDIT: I have also added a remark to the post that it is not clear if all users were MITM'd or just a subset
[1] https://techcrunch.com/2019/01/29/facebook-project-atlas/
[2] https://techcrunch.com/2024/03/26/facebook-secret-project-sn...