UFOs = Test Planes
Why would you send test planes against a US Navy carrier battle group, twice and risk damage to that group and or your test vehicle? You would have to assume they already know what can and cannot track the test object and why risk 6K people in the battle group seeing it when you can fly it over area 51 or the like and do the same tracking test?
I suspect they really do not know what these objects are and this is their way of CYA. Hey we told you and if there comes point in the future there should be an acknowledgment of these craft the USN can say we warned you.