To recreate:
1. Create a "Multi-configuration project" job type
2. Add new Axis "Sauce Labs WebDriver tests"
3. Select "Windows XP Google Chrome 44"
4. Select "Windows 7 Firefox 40"
5. Run some tests

Result:
SELENIUM_PLATFORM is set to:

• "Windows 2003" for Windows XP when should be "Windows XP" as correctly shown when using https://docs.saucelabs.com/reference/platforms-configurator/#/
• "Windows 2008" for Windows 7 when should be "Windows 7" as correctly shown when using https://docs.saucelabs.com/reference/platforms-configurator/#/

Note the platform inconsistency could not be limited to the 2 listed cases here so might be a good idea to revise them all.

More visual info in attached screen shots.