I hope you do not "do" electronics warfare for a living these days. Frankly, you do not know what the heck you are talking about.
A corner reflector is just that, a freaking reflector! It is very useful to enhance small radar return objects like sailboats and buoys (why you see them on masts so often, duh) and as markers for radar ranges. Because they have a very predictable sigma, they are very useful for RCS measurement calibration. They also have the convenient feature of returning that strong reflection over wide incoming angles, unlike a flat plate, so positioning is not critical.
And yes, I did spend decades really doing this stuff. What you might be confusing things with as far as focus is a parabolic reflector, another thing entirely, and part of an antenna or telescope normally. Such a thing needs precise aiming, so unlikely to be carried up by balloon with no means of angular positioning.
I dimly recall Jasik showing a simple monopole mounted in a corner reflector as a moderate gain antenna, but never saw one in 45 years in the business. Too many other reflector types work far better, no one bothered.
Actually I do, although I may not have articulated it well. I'm perfectly familiar with the purpose of a corner reflector. In martime settings such as the one in the second image, the purpose of the reflector is to produce a much larger radar signature when swept. For a small civilian craft, that would be likely used to make itself more likely to be noticed by larger ships' radar, so as to help avoid collision.
An example of a use in electronic warfare in a martime setting is similar to deployment of chaff, where you deploy the reflector away from the ship in the hope that the oversized radar signature of the reflector draws away an inbound missile using active radar homing.
I may not know what purpose the (likely) corner reflector in the first image was put to, but looking at the debris, it appears to be the remnants of such a device or something similar.
Or are you saying that the junk in the first image is instead actually the leftovers of a crashed alien craft?
Meh