May as well call it what it really is, a “Jacket Sleeve Holder Backer”.
The first time you hit your bare arm with the string on a full power hunting bow, you’ll remember it for a week! It’ll only take about 2 seconds to remember how painful it was.
I usually don’t wear an arm brace, I shoot a low power bow, I shoot very infrequently, I almost always have sleeves. If I was more seriously interested in “Big Game Hunting” I probably would have an arm guard of some type.