That CGO-ET information was based on Carolina Dronz understanding at the time. Now it has been found found to be incorrect.
Here's the word today from the owner and President of Carolina Dronz, with his permission:
“Yuneec is currently working on updating the FW on the CGOET cameras, they mentioned couple weeks it will be available”
For anyone planning to buy a CGO-ET for a 520, be sure to ask/tell the dealer to verify it will work with 520s.
If you have an existing ET, wait until a firmware upgrade is available to use it with the 520.
The ET will then not work on 480s.