DSC Script Resource $using:Key bug

TestConfig.ps1

Configuration TestConfig
{
    Import-DscResource -ModuleName 'PSDesiredStateConfiguration'

    $Key = "My Value"

    Node localhost
    {
        Script TestScript
        {
            GetScript = {
                Write-Verbose "`$Key value is $using:Key"
                # NoOp
            }
            TestScript = {
                Write-Verbose "`$Key value is $using:Key"

                if ($using:Key -eq 'Credential') {
                    return $false
                } else {
                    return $true
                }
            }
            SetScript = {
                Write-Verbose "`$Key value is $using:Key"
                # NoOp
            }
        }
    }
}

TestConfig

Run this script and then inspect the output TestConfig\localhost.mof file. "My Value" is not present.

PowerShell 5.1.18362.145

Changing key to mykey seems to work ok, but i get the same result using key as a variable.

Configuration TestConfig
{
    Import-DscResource -ModuleName 'PSDesiredStateConfiguration'

    $myKey = "My Value"

    Node localhost
    {
        Script TestScript
        {
            GetScript = {
                Write-Verbose "`$myKey value is $using:myKey"
                # NoOp
            }
            TestScript = {
                Write-Verbose "`$myKey value is $using:myKey"

                if ($using:myKey -eq 'Credential') {
                    return $false
                } else {
                    return $true
                }
            }
            SetScript = {
                Write-Verbose "`$myKey value is $using:myKey"
                # NoOp
            }
        }
    }
}

TestConfig