That’s unusual for a Sheltie. I had an ‘oversized’ one who was somewhat stoic, but never barked at anything but cats and door knocks. Knew someone who bred show Shelties. She had 15 IN her house, at once. I visited, as a stranger, and was enthusiastically welcomed by all but one, blue merle, male. He was standoffish, but eventually got in bed with me-along with two others. IMO Shelties are the most near-human thinking dogs around.
I agree, and not only that, they're incredibly intelligent, sensitive and perceptive. When mine chases something around an object, for example, he always runs around in the opposite direction to head it off. If he were a killer he could have as many rabbits as he wanted, but there's no killer instinct in him.