If a distinction was drawn (by SCOTUS or Congress) between search results (where you ask the platform to produce a ranked list based on search criteria) and recommendations (where you theoretically didn't "instruct" the platform to show them), I could see platforms adding a little modal to the signup flow being like "please instruct us to show you recommendations" and maybe surfacing a few settings for that, so they could later argue the recommendations were only served at your request (and thus should get search-result-style protection).