Look at that article again. Some early form of the horse collar may have been around in China around AD200-250, but the finished form wasn't until 450-500. Rome fell in 476.

Besides, consider what kind of contact Rome had with China. Nobody traveled all the way from Rome to China; instead, goods were relayed: China to India, India to Arabia, Arabia to Constantinople, Constantinople to Rome. And the caravans through Arabia didn't use horses; goods were carried on camels. So there was no route for the horse collar to take, as a live technology. Somebody in China could have tried exporting horse collars, but it wouldn't have worked--only very valuable items were worth shipping all that way.

Europe didn't adopt until 1000AD.

We weren't talking about Europe, we were talking about the Roman Empire.