This isn't my experience, at least for YouTube. If I'm not logged into Google I only see "recommended for you" video links when I'm not in private browsing mode.
Harder to tell for Google Search - unlike YouTube I never see any indication that search results are based on my history, so any manipulation that's happening is opaque (I never search while logged in, so I don't know if the behavior is different in that case)
Harder to tell for Google Search - unlike YouTube I never see any indication that search results are based on my history, so any manipulation that's happening is opaque (I never search while logged in, so I don't know if the behavior is different in that case)