I know what Ran is saying and though Ran has been quite annoying to me, Ran is right in this. Mandarin is a group of dialects in itself i.e. Mandarin in itself is French in Paris, French in Avignon with thick Italian accent and French with the Quebecois accent whereas Standard Mandarin is BBC Received Pronuciation of English, no one's mother tongue but it is a Received Standard.

However, I see the frustration with this categories too. I think it is best to translate beifanghua literally as Northern Speech (Mandarin dialects) . Putonghua as Common Speech (Mandarin-Received Pronunciation), Guoyu as National Language (Mandarin-Received Pronunciation), Beijinghua or Jingyu as Beijing Speech or Imperial Tongue (Mandarin, prestige-variant).