Is this behavior expected? I would imagine it would be a privacy violation in a multi-user system. I thought they had some sort of encryption for hiding the sites that I visit.
BTW, FF does not do this on private mode. But still it is concerning, that any program can know about the sites I visit just by looking at ~/.mozilla/profile/storage/default.
Generally, no. If a person has access to your home folder, it doesn’t matter if site-data is site-data or some UUID, the person can still look around and find that data. How to do so would be on the internet, in the source code for Firefox.
Firefox simplifies its engineering efforts and makes site-data clearly visible to the proper user by relying on the system’s security measures instead of inventing its own bespoke ones.