It can most certainly be used as a base benchmark for your system, jut not for Terragen 4 compared to other systems, especially when not employing it's new features.
But it is pretty "complete" for TG3, and thus, could be useful here.
I think the point of the TG3 benchmark specifically for TG3, was to ensure quality of time across systems. As a 1hr render on one system, and than 12hr (I imagine something like my old netbook lol) on another would, without a doubt, label that system as sub-par.