[angvelem]

И не может, Strings - одномерный массив:

property Strings[Index: Integer]: string; default;

Description

Use Strings to read or modify the string at a particular position. Index gives the position of the string, where 0 is the position of the first string, 1 is the position of the second string, and so on. To locate a particular string in the list, call the IndexOf method.

In Delphi, Strings is the default property of string list objects. The Strings identifier can be omitted when accessing the Strings property of a string list object. For example, the following two lines of code are both acceptable and do the same thing:
MyStringList.Strings[0] := 'This is the first string';
MyStringList[0] := 'This is the first string';

Можно написать:

Код:

Temp.Strings[i]:='a';
Temp[i]:='a';
Temp.Strings[j]:='a';
Temp.[j]:='a';