Can I use Moodle pages from the XAMPP Installer to upgrade a production server?
Yes, of course you can. There is no difference between the two in the Moodle PHP pages, just the environments in which they sit. If you have the patience and the understanding, you can reverse a XAMPP installation and remove XAMPP altogether, or rather, extract Apache, PHP, MySQL and Moodle from the XAMPP shell, and it will still run. Why bother, it is easier to just install Apache, MySQL and PHP as standalone applications.