I’ve read that about ACD’s, they’re on my list of possibilities if and when I get a dog.
For now, my cat rules the roost. And she is one heck of a guard cat, too! Some workmen were fixing the electicals on the side of the house once, as soon as they got near the porch she turned into a snarling, yowling monster. Which was quite a surprise, because she’s usually such a people-cat.
ACDs are great. I have one. Strong herders.
My brother has had two female ACD’s. They were/are both “at your heels”, loyal, one person dogs. They get along well with family, but tend to stick to their master and are a bit aloof. He wouldn’t own any other dog.