I agree with TrakHack that "hot" is in the eye of the beholder.
This may not come across correctly, so please bear with me: I think that "hot" is often used about horses (at least out here in KS) in the same way "bi***" is often used towards women, if that makes any sense. Again, no offense intended.
Hmmm. Yeah, I don't automatically equate hot with sensitive. My older boy is ultra-sensitive and can get worried easily but he's usually quick to trust me when I tell him he'll live. He will always come back down from being spooky, although he has a BIG spook. But he's got a quiet nature and we tend to communicate softly with each other, if that makes sense. Nervous, handsy people make him very unhappy and anxious, but not in a "I'm going to take off!!" way.
My previous horse was more like what I would think of as hot- he was like a muscle car, and had an engine you could practically hear. Our communication was constant and sometimes very loud (I don't mean animal communicator stuff, here, I'm talking about the normal discussions riders have with their horses through their aids, voice, body language, etc). He was extremely busy in his brain and body and I was always roping him back into paying attention.
You can take a line and say it isn't straight- but that won't change its shape. Jets to Brazil