An environment has been upgraded to R81.10 and the decision has been made to use Autonomous Policy for TP.
From that moment, the UserCheck page for Threat Extraction reverted to the default built-in one if the user wishes to download the original document.
I've checked the documentation and can't seem to find a reference on how to specify it. There are references to UC on TP Blades in "Manage & Settings" but it's only for Approved and Cancel.
The log entry makes reference to the "Perimeter (recommended)" profile but since it's a built-in item it's not modifiable and doesn't appear in the list of profiles.
If I switch back to custom TP, the correct UC page appears since I can specify it in the Threat Extraction tab.
So, I wonder if it's for now supported to modify the UC page for this blade when running Autonomous Policy.