This model dependence owes much to how modern central banks define their mandate, and to how monetary policy transmits to the economy. The ECB, for example, aims at preserving price stability over the medium term. That is, we define our mission in a forward-looking manner.
In fact, risk harmonization is limited because transaction costs, viewed in a broad way, are quite material in many markets. A broad notion of transaction costs includes not only the direct fees paid when transacting and trading but also the full set of risks that are involved when arbitraging among markets.