Even if that is the case, as long as long-term inflation expectations are meaningfully positive, the real interest rate will fall below the natural rate of interest, which is around 0 percent, by making the real interest rate negative. In this case, monetary policy should be effective, and Japan's economy should be able to get out of deflation equilibrium.
The distinction between time-based and data-based guidance is an important one, and the potential problems with time-based guidance are real and well described in the paper. That said, I am not convinced that this distinction has played a central role in determining the successes and challenges of FOMC communications in this remarkable era, or that it helps us improve in the future.