Some dogs will never "get it" - like the greyhounds you mention! Other dogs seem to know their boundaries, and stick to them. Our Saint Bernard, Freckles, knew where "her" yard was, even if it didn't exactly match the property boundaries on the deed! And if we were outside, she'd never be far from us. But Gracie, our Great Dane, had no such notions, and if she managed to sneak past us without us snagging a collar to put her on her chain, she'd fly off, and pause once at the crest of the hill in the neighbor's yard to say "Ha!" and off she'd go! Thankfully, she stuck to the woods, not the roads, and always came back safely. It really varies dog to dog.