When they talk about documents it's more about Google docs (sheets, ...) created internally by employees.

Getting access to personal information within Google is very, very difficult - it's not like you can query the user's sql table and get all the PII. Everything PII related is highly protected.

Internal documents though are created on a "public to all" basis - e.g. let's say you create a document with some ideas or issues with the next Pixel phone. This doc would be accessible by anyone in the company by default (you can obv change that).

It's an awesome philosophy if everybody plays by the rules and doesn't leak stuff to the outside world. Sometimes people create "Ideas Docs", "Best practice docs", "Design Docs", "Algo Docs" etc, and then receive feedback from random Googlers which accidentally stumbled upon them. It's also a fantastic way of knowledge transfer as anyone can look up the design doc for problem X of product Y and read about it.