1. A poor boy from Guangdong province, he arrived in Hong Kong in 1960 aged 12 as a stowaway.

这句的A poor boy from Guangdong province，是一个名词词组，但包含多种信息，例如这个男孩的家境情况和居住地，属于介绍人物背景的一个短语，可以理解为背景状语。可以转换为一个并列成分：

He was a poor boy from Guangdong province, and arrived in Hong Kong in 1960 aged 12 as a stowaway.

如果改为现在分词短语，那就改变了它的作用，变成原因状语？时间状语？条件状语？都不符合句意要求。

Being a poor boy from Guangdong province, he arrived in Hong Kong in 1960 aged 12 as a stowaway. (?)

我举两个例子说明这个问题：

A skilful hand at improving tools, Mike helped to make a new type of cutter. 

An excellent teacher, he has special abilities to teach his students.

这两句都可以加being，变成现在分词短语做原因状语，因为两个名词词组与后面句子存在着因果关系：

Being a skilful hand at improving tools, Mike helped to make a new type of cutter. 

Being an excellent teacher, he has special abilities to teach his students.

等于：

Becuase he was a skilful hand at improving tools, Mike helped to make a new type of cutter. 

Becuase he is an excellent teacher, he has special abilities to teach his students.

特别说明：第一句不属于“偏置结构”，因为偏置结构的名词是需要特指的，其主要功能，就是为了简化句式和强调某种信息，即强调突出句子主语。这时，该名词一般是专有名词、加定冠词、指示代词或物主代词，予以特指。

2. The descendant of Turks, who experienced a peripatetic childhood amid chaotic family circumstances, he treats the British ruling class with a combination of contempt and deference similar to Disraeli’s.

这句可以理解为“左偏置结构”。有定冠词和定语从句修饰，表示特指的名词。

关于两句的冠词能否改动的问题。我认为，都不能变。第一句是未知信息，不能特指；第二句是已知信息，必须特指，且符合偏置结构的要求。