That doesn't say your drone 'will' be confiscated. Thats very strong language.
The letter says 'maybe' retained.
FYI I have been travelling in and out of the UAE both Dubai and Abu Dhabi with my drone in checked luggage with no issues at all. Checked luggage is x-rayed in the baggage areas before reaching the claim areas. If there is something serious they will retain the luggage and inform you or have it opened by you at the exit point where you go through the customs again through nothing to declare or goods to declare. Drone doesn't have to be declared to customs. You are not allowed legally to fly it in UAE without GCAA registration which is only available to UAE nationals and expat residents.
This is the latest as of today from the UAE GCAA drone user manual
UNMANNED AIRCRAFT/DRONE USER MANUAL
● Your Drone must be registered before conducting any flying activities.
● Drone registered under your name is your responsibility.
● All UAE laws and regulations must be followed while operating the Drone.
● Manufacturers Operating manual must be followed for safe operation.
● Drone operations only allowed within the flying zones, not exceeding 400ft above sea level
● With no exceptions, No Drones are allowed to be operated near aircrafts, airports & helicopter landing sites.
● Also, Drone operation is not allowed above individuals, public and private & public properties or in a way which may endanger individuals or their properties.
● Ensure your Drone is operating within your line of sight. You must immediately land your Drone if you see or hear any aircraft or helicopter.
● Drone users are strictly prohibited from breaching others privacy. Failure to comply will lead to penalties stipulated in UAE law.
● Camera usage is only allowed in the flying zones. Drone users must not violate relevant UAE laws while using the camera.