It seems to be someone's talking points or more charitably a meme (differentiated by how organic the idea is). The publisher/platform dichotomy is a flat out wrong myth which keeps on being repeated - and often from high places.

I would call it outright propaganda at this point because the dogged insistence on not listening to objective facts seems more "big lie" style opinion shaping than mere ignorance which has caught on. At this point I reflexive downvote all who repeat it uncritically as "fact".