This very well could be true. The reason there is not standing corn in front of the combine header is because you will back up to work on the header if there is a problem. I would call having a deer in the header a problem. As far as no dust on the header, if you have a big enough of a breeze from the right direction there will be very little dust. If you have a big enough of a wind, you have just increased your chances of putting an animial in the combine (hard to hear the machine over the noise of the rustling corn stalks). It appears the buck was still alive while in the header (legs are caught), and they cut the throat to kill it.