Maybe you have a very knowledgeable and experienced agent. But odds are most of them have never dealt with an issue of a vehicle being over GVWR, so they're just guessing.
People can say whatever they want about things that may or may not happen in the future. All that matters is what's written in the policy.
Read through all of your insurance documents and keep them in case you need to refer to them later. If you don't understand something, seek clarification from a knowledgeable third party. Don't trust anything the insurance company says.