Those sponsored posts appear next to whatever appears in the user's feed. If a user follows a bunch of cat photos, then the sponsored post appears next to cat photos. If the user follows a bunch of NASCAR related accounts it appears next to NASCAR. The ad company has little agency over this.

I don't think advertising companies would really see this as an issue. It's not like an ad playing before a video where sponsorship can be directly tied to a piece of content. The content adjacent to ads is determined by users' viewing habits and follows.