In the fabric.mod.json, the mod would no longer require all modules of the Fabric API to be installed, but rather just referenced ones (command, event, etc.)
Although this wouldn't affect 99% of people, when developing solely with this mod it would speed up build and compile times.

In reality, as this mod is usually developed with other mods for compatibility or performance reasons, the entire Fabric API is always needed, so this would just hinder development.