as far as放在age 前面,并没有“就”的意思,
就他的年龄来说,----可以可用according to,环境不同,还用同一个词会弄巧成拙
has been也不恰当,直接用is就够了,in height有点多余,直接改成tall,and改成but,so tall后面有了修饰的成分,你又加that-clause就不行了,要么去age部分,要么去that部分
He is 1.8 meters tall,but I think he's too tall according to his age这样就可以了,再加it's not to be expected就显得意思重复多余了