A lot of stuff is not proven, otherwise no need for science. I am giving you a little insight, not fiction from a novice.
You are not picking up on the subtleties of chicken language. Call you are picking up on indicates something above. I can often pick up on above object just flying over, object approaching, or even object coming in directly at you as well as proximity. Visual ques from signal giver gives information on direct.
I live in an environment that has lots of stimuli and I work around chickens in extremely close quarters, much closer than a field biologist so I can pick up on same stimuli from same perspective as the chickens. Some of the signals are intended only for those in close proximity to you, others calls are for birds farther away and some calls are for the predators ear specifically.
As I zoologist, I have good handle on the importance of perspective that is often overlooked by a human observer trying not to interfere with subject animals.