If they were to send out replacement parts on verbal request alone then they would see their warranty parts expense skyrocket as they would be buying switches, and motors and bearings for every tool in the shop.
If you buy an alternator or starter for your car and it goes bad would you expect a parts store to offer a replacement without you bringing in the old one for a bench test? Why should grizzly be any different?
One policy many companies use in your situation is they will take a credit card number as a deposit. If you return a bad part to them within thirty days there is no charge. If the part is good or you never return the bad unit you are charged for the part. If they don't have that option it should be put in place. All return policies are not created equal, however they are in writing and available.
Extremely liberal return policies are expensive. The main selling point of Grizzly tools is that they are cheap. I have never ordered a grizzly tool but I have worked a lot with claims. You wouldn't believe the amount of fraud. Sad but true.