This part caught my eye.
These objects include birds, balloons, recreational
unmanned aerial vehicles (UAV), or airborne debris
like plastic bags
It never occurred to me how utterly "alien" a wind-borne plastic bag's behavior might seem on radar.
A constantly shifting radar cross section, sudden directional changes no "actual" flying craft could manage, etc. After all it's an object with significant surface area but nearly zero mass being buffeted around in a region of the atmosphere with swirling wind currents.
Depending on the angle, the radar cross-section of a modern stealthy aircraft is reportedly about the same as a small bird or even a bumblebee. So the radar cross section of an airborne plastic bag or balloon would be pretty similar.
That said, I think the visual reports and videos from military aviators are pretty clearly describing something else.