Kinda, but they also don't really realise that they have much more control over the feed than they expect (in certain areas)
For the reel/tiktok/foryou-instagram feeds, it shows you subjects that you engage with. It will a/b other subjects that similar people engage with. Thats all its doing. continual a/b to see if you like what ever flavour of bullshit is popular.
Most people don't realise that you can banish posts from your feeds by doing a long press "I don't like this" equivalent. It takes a few times for the machine to work out if its an account, groups of accounts of theme that you don't like, and it'll stop showing it to you. (threads for example took a very long time to stop showing me fucking sports.)
Why don't more people know this? because it hurts short term metrics for what ever bollocks the devs are working on. so its not that well advertised. just think how unsuccessful the experiments in the facebook app would have been if you were able to block the "other posts we think you might like" experiments. How sad Zuckerberg would be that his assertion was actually bollocks?