I did that from iOS 13.2 to iOS 13.1.3 a few days ago and it didn’t work. My iPhone was updating a while but stopped loading and I couldn’t start my iPhone anymore. Tried it 2 times. Either I’m asking myself if the downgrade is necessary from iOS 13.3
THIS is the issue I always run into.
That’s why I always have done the DFU/Recovey Mode and Restore. I guess whatever works lol