the F-35 would be “four times more effective” than current fighters in air-to-air combat,
Hmmm
. When that statement was made "current" meant 3rd and 4th gen fighters. And it is.
Of course this depends on the definition of "effective". In this case it does NOT mean one-on-one against a 4th gen fighter in a close-in furball. F-35 probably only holds a slight edge in that scenario. But over the full spectrum of air-to-air combat, the F-35 meets or exceeds its design objectives.