I read into it some more and I guess it has to do with whether it's a bonded neutral or floating neutral. My Generac XT8000E appears to be a bonded neutral, as far as I can tell. But then it also depends on if the panel is a bonded neutral? If they are both bonded neutral then it says you need the rod so that in the event of a faulty appliance, the power isn't sent back to the genny, making the frame live. If both are neutral bonded, you also have the risk of parallel power, where the fault from an appliance goes back to the neutral and ground on the panel but then also back to the neutral/ground on genny, and the ground isn't meant to handle continues power, so it could cause wire failure. But I'm hoping our electrician set up the transfer switch to separate the neutral/ground bond when it's being fed by the genny. Here is the article I found that really spelled it out nicely. https://homebatterybank.com/do-i-need-to-ground-a-generator-simply-explained/