关于新概念二册第四课的问题I have just received a letter from my brother,T

关于新概念二册第四课的问题
I have just received a letter from my brother,Tim.He is in Australia.He has been there for six months.Tim is an engineer.He is working for a big firm and he has already visited a great number of different places in Australia.He has just bought an Australian car and has gone to Alice springs,a small town in the centre of Australia.He will soon visit Darwin.From there,he will fly to Perth.My brother has never been abroad before,so he is fending this trip very exciting.
这是课文
我的问题是这句：He has been there for six months
havehas been 不是去过某地现在已经回来了吗,可是课文中他的弟弟还没有回过,为什么用has been