Purpose of the question
I want to validate the following:
API call performed
If i call: https://learn.microsoft.com/en-us/graph/api/driveitem-permanentdelete?view=graph-rest-1.0
This will permanently delete the document as described in the documentation.
Question:
Does this also mean permanently for the secondary recycle bin ? (assuming yes but just to know for sure).
As you presumption is correct, it's a permanent delete and file is not accessible from second stage recycle bin.
You can check the second stage recycle bin
https://{tenant_name}.sharepoint.com/sites/{site_name}/_layouts/15/RecycleBin.aspx?view=13