Sultan (ICAO code AUH) is the designated callsign for the Presidential Flight of the United Arab Emirates (according to Designators for Aircraft Operating Agencies,
Aeronautical Authorities and Services (Current Edition: 151)).
OK then, so they were wrong in what they had on their FMS/Mode S config, it should have been AUH3 instead, as I am sure that their FPL was filed as AUH3. No problem with Sultan 3 being their radio callsign, but radio callsign and FPL/Mode S callsign is a totally different beast, at least for civilian aircraft.
Cause with the military it's a whole different ball game, if you factor in their funny callsigns. I once heard a bunch a mil jets during an exercise, and their callsigns where themed after car makers, so you had on the same frequency Audi, FIAT, Mercedes... when the KC-10 tankers were based out of Malpensa during the first Gulf war in 1991, they were flying south to refuel their aircraft somewhere over the channel between Sicily and Sardinia, and the callsign they were using was "Pasta"...

Ciao, Luca