I went ahead and called the outfitter last eve. Here is what I found out. He said the area that they hunt hogs is swampy and has los of thick underbrush. So they tell people to shoot them right behind the ear, so they drop immediately. I can see his point. If I were an outfitter, I suppose I wouldn't want to be crawling through the brush trying to find a hog either!
What county are you going to be hunting in?
As for the boar losing his shields if castrated, I've killed sows with calloused "shields" on them that were 1 - 1.75" thick in the state the OP is going to be hunting in. These pigs around here inhabit areas that are so thick visibility is measured in feet. Some areas you have to get on your hands and knees to get through or back out and find another way.
That said, they aren't bulletproof if you put the round where it is supposed to go. My .243 is my go to rifle for pigs when in a stand. I'm looking forward to putting an arrow in one too, just not in the shoulder area.