When agents fail to update, they make decisions based on information that is to some extent out of date. The updating is staggered across the population, so that at any one time some people are paying attention to news, while others remain inattentive. As a result, information diffuses gradually in the economy. The average forecast responds slowly to news, as in the data.
Each individual makes the best forecast given their information. At the same time, however, the average forecast error across agents can be predicted by the ex ante revision in the average forecast, as in the data. Finally, again in line with 1/4  BIS central bankers' speeches  the data, agents in the model disagree, because their information sets differ.