Angola Friendly?

I read over on the Angola blog that their football federation has announced that they will be playing the Socceroos in a friendly in Germany before the start of the World Cup. This raises two questions. First, why would Australia want to play an African team that plays nothing like its World Cup opponents? Second, where does this game fit into the friendly schedule already announced:

May 25: Australia v Greece
June 4: Netherlands v Australia
June 7: Liechtenstein v Australia (not confirmed yet)

If this is a replacement for Liechtenstein then I have no problem with it since both teams are beatable and should give us some goal scoring confidence heading into the World Cup. But if this is another game to the list then I think it is unnecessary and that it puts our players at undue risk for injury.