A good thread to mention Lemmy in - a Daily Show segment about social media companies, most of the commenters don't seem to realize that nonprofit social media exists!
The fact that "non-profit social media" exists is not nearly enough to disprove the technical veracity (the best kind of correct, after all) of the accusation that the overall technology does target, modulate, and commodify interaction — regardless of the eventual use of said data.
The technology of social media is just writing + ways to find it. The criticisms being leveled apply way better to the narrower technology of large scale, opaque content algorithms (which for most are indistinguishable from social media because the only use platforms that have it).
While I don't discount the veracity of your specific example, its existence doesn't diminish the societal threat that is the accepted mode of social media itself.