No, the rules remain the same
Plain and simple...the upgrade version of XP will check for legitimacy of the user to install said upgrade.
If the prerequisite O/S is not detected during the initial check...then the user must insert a CD reflecting the qualifying O/S.
You may want to read Clean Install Procedure with Illustrative Screen Captures - http://www.theeldergeek.com/xp_home_install_-_graphic.htm
, this deals with a clean install from an upgrade CD.