We've had a report about batch loading not working with mutations, which seemed counter intuitive since query and mutation should work the same way for field selection. On closer look, however, DataLoader does expect AsyncExecutionStrategy while mutations execute with AsyncSerialExecutionStrategy. That's probably related to the requirement for serial execution of mutations, but still, batch loading not working seems more like an unintended side effect. It would be good to make this work if it can, or otherwise clarify the limitations, and update the DataLoader documentation accordingly.