I doubt the description is correct, or it must have been very badly auto-translated. EA would never praise their own animations like that :)
That said, I never thought of horses possibly being restricted to one lot or trails, but it could actually be likely. Re cars, I never understood what my sims would use them for as the world is not open like in TS3. Same goes for horses, we should expect some sort of arena to use them, being a sports venue or ranch. Yes, they could benefit from the hood's common ground, but probably not without routing issues as they would meet Judith Ward ad Nancy Landgraab frequently, and those ladies would not be interesting in stepping aside to let a horse pass on the path. So, a riding trail in a new world, a horse racing arena (will most likely be rabbit hole), and your ranch might be it. I'm actually more concerned with what lots would be large enough to keep a horse if they are stuck to that lot. A stable and a field might get into only a handful lots... Can we hope for a communal ranch where your sim just rent one slot in a stable for their horse? I guess that is how it often works in real life. So many questions :)