Hello
The Allow Auto User Creation parameter available through the web UI and octopus.server.exe is missing from the DSC.
Web UI:

DSC:
param (
[Parameter(Mandatory)]
[ValidateNotNullOrEmpty()]
[string]$InstanceName,
[Parameter(Mandatory)]
[boolean]$Enabled,
[string]$ClientID,
[string]$HostedDomain
)
I have a PR ready to go if it's fine for you
Thanks