There are cases where restrictions have an additive rather than multiplicative effect on the reproduction number, but after better modeling they often end up as

There are cases where restrictions have an additive rather than multiplicative effect on the reproduction number, but after better modeling they often end up as ultimately multiplicative. For example, let's say you observe "closing schools" to bring Rt from 3 to 2.7, "closing offices" to bring Rt from 3 to 2.3, and "closing both" to bring RT from 3 to 2. What's really happening is not that the two restrictions have a -0.7 and -0.3 effect. Instead, the two apply to almost disjunct subsets of people. Therefore it is more accurate to say that the "closing both" restriction is a *0.66 reduction of the reproduction number, while "closing schools" and "closing offices" only apply that 0.66 factor to a subset of the population. What is really additive is the amount of people affected by the restriction.