Yes those diagrams exist, but you've got to remember that these components are constantly changing as well as new components being added and others being removed all the time. It's a beast and perhaps I was a little liberal with my assertion that "NO ONE" understands it. It's possible to understand at a high level: eg "...and then the posts get filtered through this ranking component"

But then that ranking component can change week over week so if you thought you understood all of the ranking mechanics last week, then you probably have some catching up to do this week.

There's also a lot of people working on this so stuff changes fast and often. Think about all of Facebook's different products vyying for attention in the feed. Think of all the PMs with agendas who want their product in the feed in certain ways.