I've never seen any type of warranty for DJI products that allows customers to dissemble the aircraft to remove the defective part, send it in, get a replacement, and repair it on their own. There are likely many reasons this process works like this -- here are a few:
Repair work done by an unauthorized party can void the DJI warranty
It would be impossible for the warranty provider to confirm the part in question is the problem
It would be impossible for the warranty provider to test the aircraft after replacing the part
Allowing the warranty provider to do all of the work could eliminate a lot of potential back and forth
Customers could break other parts while attempting to remove the defective part
Customers could abuse the system by sending in parts from aircraft not covered under warranty
If you want to the real answer, you should probably ask Expert Drones.