Token could return a different value than the one used by system.module

token.module could return for the token site-name a value that is different from the value used by system.module.
This is because token.module uses the following code to get the value of the Drupal variable site_name:

variable_get('site_name', t('Drupal'))

while system.module uses the following code:

variable_get('site_name', 'Drupal')

This means that for web sites which don't have the variable explicitly set system.module will always return 'Drupal', while token.module returns the localized version of the string.