Update 1:The reason for the QF-4 not being shot down is probably that the test was not a test of the AIM-120 missile’s ability to hit a target (something that has been proved in the past) but on the F-35’s ability to track the target and guide the AMRAAM until this reached the kill envelope. Once the missile starts self-guiding to the drone the test is accomplished and there is no need to waste a costy unmanned aircraft: the AIM-120 is directed to self-destruct before impact.
GR, did you bother to read the article? This is from the article, FWIW.
Is it fact or speculation? Don't know, but it makes a certain amount of sense.
Just out of curiosity, how much test flying and weapons testing have you done? Test programs are a thing of their own.