Correct. It's all fictional. Choose your own adventure.
Look, while most of the setting background material is presented as historical documents or reporting, and thus must be taken with a grain of salt, anything not so presented is different, especially if it's framed as referee's information, as was done in the MegaTraveller Imperial Encyclopedia with the player section and the Referee's notes. That is how you know what is what.
The brutal truth is that no one can ever actually know all the facts. Even a typical city has too many people to fully document, too many secrets to fully expose, too many transactions to account. Everyone has to abstract things just to get through the day in real life, let alone in a game with thousands of planets.
But we can discuss our opinions on it all, just as researchers discuss their data and source documents. Useful conclusions can be drawn from that.