In how far are these functions different from the existing string class? ... could you reformulate the question please?
In the core of Arduino there is a file called Wstring.cpp with all the string code described here (mostly) - http://arduino.cc/en/Reference/StringObject -
Some functionality is allready available in the string class e.g.
int FindStr(String Str, String SubStr) versus String.indexOf()
int StrToInt(String Str) versus long String::toInt() // not documented but in the class!
String ReplaceStr(String Str, String Replace, String ReplaceWith);
ON the other hand these two are new and useful.
int FindStrPass(String Str, String SubStr, int Passes);
int CountStr(String Str, String SubStr);
On the other hand the functions treating the string as a separated list is a nice self contained set of functions.