The concerned is one of consistency in how media is regulated. E.g. Facebook, is the worlds largest media company, and it truly acts and behaves as a publisher now. It acquires its content from an army of paid and unpaid providers. They may be individuals, often they are influencers, often they may be nefarious agents and companies. It then decides how to place that content in it's "publication", which just happens to be an app and website. It goes out and tells the market, "I have this great publication in which you can place ads!". It then sells ads to those people, and makes a decision on how to place those advertisements inside its publication alongside that content that it acquired.
So how is it not a publisher? And why should it be regulated to any kind of different standard from other publishers?