In the case of demand shocks, there is not a material conflict between the real and nominal 2 / 14  BIS central bankers' speeches  objectives, as the monetary response is effectively the same. That said, the flexibility of the target potentially allows for greater inflation variability to achieve lower variability in the real economy.
First, market information is unavailable for many banks, often because they issue public debt only infrequently. Second, market discipline for banks is somewhat dependent on the Federal Reserve's policies and actions, and thus it has a "mirror problem" of its own.