I have had one like this. Wonderful horse under saddle and in general excellent ground manners but hated being groomed. Was a TB long off the track when I got him. Particularly hated currying. He would stand still, but his skin would crawl and he would pin his ears, wring his tail and make faces. He made it very clear you were annoying him, but he was too well mannered to do more than that. Tolerated a soft body brush used gently, but tolerate was the operative word.
My compromise with him was to keep him body clipped (I sedated him to clip because that was annoying as heck to him as well), keep a sheet on him, and to go over him quickly with a hot towel before riding.
I had a wonderful groom at the time who was professionally offended by a horse that didn’t enjoy being groomed and she experimented with every grooming tool and technique she could find. One day I walked into the barn aisle and found the two of them; he was completely relaxed, one leg cocked, head down, licking and chewing. The tool was a tiny, soft gel curry with small teeth, and she was using it very gently, sort of as a massage.
In his case, it was truly a case of sensitive skin, and maybe the overhandling at the track as danacat mentioned.
I do think eliminating ulcers as a possible cause is always wise, (I have certainly known horses that were grumpy on the ground because of ulcers) but, IMO and IME, there are some horses that are just sensitive. And you can take either my pragmatic approach (clipped and in a sheet) or my groom’s sympathetic approach (scour the earth to find the correct grooming tool) but if the horse otherwise has decent ground manners, I think it is good horsemanship to find a way not to make the horse miserable with grooming.