It's just how you define "want." They a-b tested the algo vs chronological feed and the algo one because more people used it. It's just stated vs revealed preference. As a business, who's goal is to make money, does something that makes them more money, are they supposed to stop?

Whether it's good for society is another question but, users definitely didn't show that they "wanted" a chronological feed, they only said it. There was a JUMP in engagement, not a decline.

"want" is different from "will consume if offered". Arguably, the definition of "want" that most people use is one of higher-order desire. E.g. a drug addict wants drugs, but doesn't want to want drugs. People might choose a certain feature if offered and they aren't aware of its negative impact on their mental health. Then they might become cognizant of the negative effects but by then the choice to not use that feature is no longer available so they're stuck with what they have. Alternatively, the choice to not use the feature might still be present, but the neural reward pathways have already been built. The user then wants the feature, but they don't want to want it.