Using a reasonable proxy is not "pure clickbait", though it may be misleading. It adds an additional assumption about the Google results not being tampered with by Startpage, but it seems like a reasonable one, compared to the alternative of Google doctoring the search results when detecting a scraper and/or doing personalization.
If the authors have done their due diligence and confirmed the results from Startpage are actually Google results, then I don't see why they couldn't claim so in their title.
If the authors have done their due diligence and confirmed the results from Startpage are actually Google results, then I don't see why they couldn't claim so in their title.