Direct from this FAA
NOTAM:
ADDITIONALLY, DUE TO GPS INTERFERENCE IMPACTS POTENTIALLY AFFECTING EMBRAER PHENOM 300 AIRCRAFT FLIGHT STABILITY CONTROLS, FAA RECOMMENDS EMB PHENOM PILOTS AVOID THE ABOVE TESTING AREA AND CLOSELY MONITOR FLIGHT CONTROL SYSTEMS DUE TO POTENTIAL LOSS OF GPS SIGNAL.
What is so specific to the Phenom 300 when it comes to flight control & GPS ?!