Why does bread flour have lower protein content than all-purpose flour?
I would just say that you are translating the terms too literally. In the USA, it is typicall to sell flour made from hard spring wheat under the name "bread flour", because people there traditionally enjoy bread made from it. In other countries, people have different expectations of their bread, and hard spring wheat was probably not even available prior to globalization. So it is logical that companies there formulate flour to produce the locally preferred bread texture, and sell it under a term which literally means "bread flour". This is a very common linguistic/cultural phenomenon - in different parts of the world, the local term for "cheese" without further qualifiers means a very different style of cheese. 

I have never been in Hungary, but on the Balkans, traditionally, there is a preference for soft, fluffy, white bread. So I wouldn't be surprised if this Hungarian company has formulated their bread flour to produce something in that direction.