I would boot the client back into WinPE and manually verify your unattend.xml has the correct password being shown once written to the client. Below is the Audit section from my answer file with the required settings.
<component name="Microsoft-Windows-Shell-Setup" publicKeyToken="31bf3856ad364e35" language="neutral" versionScope="nonSxS" processorArchitecture="x86">
<UserAccounts>
<AdministratorPassword>
<PlainText>true</PlainText>
<Value>%AdminPass%</Value>
</AdministratorPassword>
</UserAccounts>
<AutoLogon>
<Enabled>true</Enabled>
<Username>administrator</Username>
<Password>
<PlainText>true</PlainText>
<Value>%AdminPass%</Value>
</Password>
<LogonCount>1</LogonCount>
</AutoLogon>
</component>