PSADT not correctly retrieving OS language

PSADT is not correctly retrieving the OS language. It is always returning English when the OS is French.
The AppDeployToolkitMain.ps1 uses:
[Globalization.CultureInfo]$culture = Get-Culture
[string]$currentLanguage = $culture.TwoLetterISOLanguageName.ToUpper()

If I use local powershell ISE on French machine with the above commands the OS is returned fr-FR.
But when executing the install PSADT returns:
[Initialization] :: Current Culture is [en-US] and UI language is [EN]

Anybody know where get-culture is pulling the OS language from?
HKCU\Control Panel\Desktop PreferredUILanguages? This entry is not always present

After changing the default language in Region & Language I needed to go to Administrative tab and select Copy Settings and then under “Copy your current settings to” enable “Welcome screen and system accounts”

Can you try running Get-UICulture and let me know what result you get? We may need to switch to using that cmdlet in the toolkit to correctly identify the language.