ProductKey setting in autounattend.xml at Windows Setup not being read

Question

I've been trying to use DataImage component of Windows Setup to unpack an extra WIM (aside from insall.wim) to another partition (D:) during windows installation. I needed an answer file, so I went to https://www.windowsafg.com/ for a template that I assumed works. I then stripped it down for what I need it to do, while leaving everything out so they would default & hopefully leave me with exactly the same installation experience.

Here's the autounattend.xml I prepared (my actual product key is censored with Xs):

<?xml version="1.0" encoding="utf-8"?>
<unattend xmlns="urn:schemas-microsoft-com:unattend">
    <settings pass="windowsPE">
        <component name="Microsoft-Windows-Setup" processorArchitecture="x86" publicKeyToken="31bf3856ad364e35" language="neutral" versionScope="nonSxS" xmlns:wcm="http://schemas.microsoft.com/WMIConfig/2002/State" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance">
            <ImageInstall>
                <OSImage>
                    <InstallFrom>
                        <Path>sources\install.wim</Path>
                    </InstallFrom>
                    <InstallTo>
                        <DiskID>0</DiskID>
                        <PartitionID>1</PartitionID>
                    </InstallTo>
                    <InstallToAvailablePartition>false</InstallToAvailablePartition>
                    <WillShowUI>OnError</WillShowUI>
                </OSImage>
                <DataImage wcm:action="add">
                    <InstallFrom>
                        <Path>sources\d.wim</Path>
                    </InstallFrom>
                    <InstallTo>
                        <DiskID>0</DiskID>
                        <PartitionID>2</PartitionID>
                    </InstallTo>
                    <Order>1</Order>
                </DataImage>
            </ImageInstall>
            <UserData>
                <ProductKey>
                    <Key>XXXXX-XXXXX-XXXXX-XXXXX-XXXXX</Key>
                </ProductKey>
            </UserData>
        </component>
    </settings>
    <settings pass="specialize">
        <component name="Microsoft-Windows-Shell-Setup" processorArchitecture="amd64" publicKeyToken="31bf3856ad364e35" language="neutral" versionScope="nonSxS" xmlns:wcm="http://schemas.microsoft.com/WMIConfig/2002/State" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance">
            <ProductKey>XXXXX-XXXXX-XXXXX-XXXXX-XXXXX</ProductKey>
        </component>
    </settings>
</unattend>

Yet, when I leave this autounattend.xml at the root of the installation media & then boot to it, the setup early on says it cannot read the ProductKey tag. What's wrong with my answer file?