@Carlos Guzman - Admin, Thanks for posting in Q&A. Based on my checking, I don't find the option to set the default sign in user in Windows Configuration Designer tool during create a provisioning package. Here is a link with more details:
After researching, I find the following link mentioned the registry key to change the default login account. You can test and see if it can work.
https://community.spiceworks.com/topic/2252082-setting-the-default-logon-account-for-windows-10
Note: Non-Microsoft link, just for the reference.
Hope the above information can help.
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