My Dutch Warmblood is a walk silent carry a big stick kind of guy. I have only heard him whinny if the Arabian gets taken away from him, then he will whinny up a storm, in a panic.
The Arabian, however, will whinny to greet me, to tell me to hurry up with his feed pan, or if he sees me come out of the house, he will win to acknowledge that he sees me and he knows it’s feeding time. Yes he does know when feeding time is, both horses do —- it is amazing how accurate their inner clocks are when it comes to food.
The horse in your video is looking for another horse. If you listen closely, you can hear a horse whinnying back to him in the background. That is why the horse being videoed turns around and heads in the other direction. He is heading toward the horse that is answering his call.
Also, Their whinny’s have a different tone to them, depending on what the issue at hand is. Sometimes a whinny can elevate to a scream. I have seen that happen more than once when I have had to lay a horse to rest that was a close buddy of another horse.