Some users download this mod from the Modrinth or CurseForge websites without checking for dependencies. Without GeckoLib, it results in a crash which users find difficult to understand. Putting the GeckoLib dependency in the FMJ results in the Fabric Loader mod resolver window which communicates the dependency outside of Modrinth and CurseForge.

Where to add this: https://github.com/Tfarcenim/Daves-Potioneering/blob/1.20.1-multiloader/fabric/src/main/resources/fabric.mod.json#L38