Having multiple datagen entrypoints causes them to step on each other, deleting each other's stuff depending on the order they're added to the fabric.mod.json. Using the latest for 1.21.

Im not sure this is a supported usecase atm, this is happening becuase each entrypoint gets its own FabricDataGenerator instance, when the vanilla datageneration is ran it will delete files that were not generated by the current data generator. Fixing this doesnt look to be that easy.