Looks like they reduced it to 5, because yay was not universally understood.

That stuck out to me, because those auto-video ads were one of the major reasons I uninstalled the facebook app entirely. Quickly checking some things on my phone while walking down the hall at work, or while some code runs I don't want to accidentally play some loud nonsense, and that happened often enough for me to downgrade my mobile facebook experience back to the browser. I still use facebook, but not the app.

That sort of jives with this anecdote as well:

"When the company redesigned the News Feed in 2013, it looked great on the iMacs in Facebook’s headquarters but made the product harder to use everywhere else."

Most computers aren't macs, let alone iMacs. How could you possibly miss out on testing for even one other thing? It's weirdly close-minded given what facebook is and how it presents itself.