Well of course it did. Tech researchers' reliance on "let's secretly tweak things without explaining different behavior to our unconsenting human subjects" is appalling.
What you see on a social media site is a function of how the algorithm (whether proprietary ranking or chronological sorting) operates on the connections you've chosen to make on the site -- groups you've joined, pages you follow, etc -- and the different things FB people have decided to make eligible for display ("your friend commented on this post from this page you don't follow") and the different content people have chosen to post within the ecosystem that creates. You can't isolate any of those axes!
On Mastodon I am able to follow people whose daily chatter I like and whose high-engagement content I'd find extremely tiresome, because nothing optimizes for the latter so I'm more likely to see the former. I have tools to keyword filter and it all works well. If you showed me the high-engagement stuff, I would have to change who I followed.
On Facebook I join groups where the norm for a post is extremely low-effort because if it doesn't start to resonate with people, FB just won't show it to anyone, and no one's been bothered. If you showed me the chronological feed of those groups at the high volume at which they post, I would have to leave them.
The norms about what is posted and who is followed are inextricable from people's expectations about what they'll see which are shaped by what you've been doing for years.
Why would you expect to get meaningful data from yanking the tablecloth away so all the plates come with it?