The F-35 was not "beaten". In a test about aircraft behavior in the current settings at high AoA, the aircraft flew 17 engagements with a F-16. The test pilot wrote a number of recommendations to undo a couple of current settings, which came apparent in this test. It reads that the F-35 is in a disadvantage in circumstances with a high Angle of Attack. Nowhere the report said it was beaten. A disadvantage is not the same as beaten. Also this was a flight is a series of tests to see if the flight envelope can be expanded.