The box is only unchecked because of the curious decision to allow transferring of a single prop / engine which I'm not convinced has any real value. One thing

The box is only unchecked because of the curious decision to allow transferring of a single prop / engine which I'm not convinced has any real value. One thing that isn't stated is what the state of the redundant thrust slider is when the inputs are ganged together. In the physical implementations I've seen the redundant lever is usually moved to neutral and it's not inconceivable that this was carried into the digital UI. In that case failing to spot the fact that there was a differential thrust involved because of the lack of a checkbox might be much more understandable.