If you are filing a lawsuit using a cause of action about blocking access, then you don’t need evidence of harm.

In either case, if the act is the kind that cannot avoid causing harms, then if it occurred, evidence of harm should be easy to find and put forward, at need.

More to the point of this actual lawsuit, acess or harm to the SVP businesses is not the issue in the cause of action here, harm to competition in the general search and general search ads space, where the SVPs are not competitors to Google but suppliers to Google and its competitors is. So, the lack of presentation hurting their business would not establish the required harm, what would be required is something like injury to their ability to sell data to Google’s competitors resulting from Google not presenting the SVPs in the specialized searches.