However, as discussed in other threads, if a CEE exists at the garage, it must be connected to the overall GES anyway, IMHO.
You are not required to create a ground by driving a rod electrode which was not there before. But if an electrode exists, it is hard to avoid using it.
The distinction made in the other thread was that if the required length of rebar was part of a complying mass of concrete, a CEE exists and must be used even if no provision was ever made during the pour to connect to it.
However, if there is already a CEE at the main building, there is then no requirement to connect more than one CEE to the GES. It is not 100% clear to me that this applies when the two CEEs are part of different structures though.