On the link:
At the beginning, it says that Deep Research uses “data on the public web”:
Deep research is a specialized AI capability designed to perform in-depth, multi-step research using data on the public web.
But, in the last paragraph, it says “any uploaded files across all of your conversations”:
Currently, deep research can access the open web and “any uploaded files across all of your conversations”, but is not able to access private data sources (e.g., subscription-based sources, internal resources). We look forward to making this type of data available to deep research in the near future!