Honestly, that part seems very reasonable. If a platform curates or modifies content or promotes it beyond what some system thinks the specific user might like, then yes, the platform should be responsible for that content.
The real question would be, should the platform become responsible for all ontent, or just the content it curates / modifies / promotes?
My opinion is that this should work on a per-content basis, where the platform only becomes legally responsible for a unit of content once it associates itself with it by promoting, modifying, etc. this content. Whether it is realistic to enforce it this way is, of course, another question.