Differential Data: https://<subdomain>.brightspace.com/d2l/datahub/dataexport/list/dataset/<dataset-uuid>
Data Export endpoing:
https://docs.valence.desire2learn.com/res/dataExport.html#post--d2l-api-lp-(version)-dataExport-create
Specifically, I'm seeing User+Content Topic ID pairs in the Differential data for a given day, that does not exist in the data provided by the API.