There is a lot of experimental activity going on all the time, a lot of it classified. I suspect that these very infrequent 'encounters' are not the same thing but chance encounters with different activities. A hypersonic vehicle may show up on radar, but its not something a hornet driver is "almost going to hit". Two different things.
When I fly I regularly (as in about once a year) have near encounters with things varying from weather balloons to Mylar birthday balloons.
I submit that just the opposite is what actually transpires. The Art Bell types take a sliver of info and cast a wide net claiming gov cover up. Releasing these tapes plays into that since the DoD has not released the findings of their investigations.
The F-117 was kept quite secret until it flew in operations in Central America. The Aurora Project also has been kept quiet. But the crux of my argument is this, IF what these aviators are seeing is US tech, it should remain closed off to the genpop. IF it is ET, then it should be released to the NSA for threat assessment.
Releasing to the public with no explanation is reckless.