Fossil Is Not Relational

I know some of you are tired of SQLite/Fossil topics, but I found it interesting how the creators of SQLite themselves chose to use it as a blob store and then crosslink the blob contents to an actual relational schema.

We often discuss using SQLite as a file format and Fossil is often mentioned here as benefiting from a relational store, but I wonder if anyone here has actually used this architecture instead of making their actual SQLite schema the source of truth.