Probably, in conditions in which uncertainty is high, frontloading the accumulation of a given stock of purchases more forcefully signals the central bank’s commitment to inject the degree of accommodation necessary to support the recovery. By contrast, in more normal market conditions, the market’s capacity to engage in intertemporal arbitrage improves.
Consequently, investors may become “more patient”, or, in other words, better able to evaluate the stimulus that can be expected to come from a purchase plan that is to be executed over a more extended time interval.