could it even be narrower than 'corporate social media'?

Yes and no. Yes, in that for many people it's "Fuck Facebook in particular" because of just how absolutely invasive Meta has been, and how it has specifically turned brainwashing users into a business model.

No in the sense that corporate social media will all inevitably try to do the same thing, sooner or later, because social media that's actually usable for users' interests just isn't profitable. The enshitification process demands that we be manipulated into being more reactive, more hostile, and more open to the influence and exploitation.