This is accurate because he would stop to come chase you.
If I miss, I'm likely going for an Inhibitor :p (cause I tend to Ult at close range... I'm not confident with long distance .__.)
You gotta get that long distance down. The best thing about Sion ult is not knowing for whom the bell tolls until the train is already running over your decrepit body. :D
Very accurate, when i dodge Sion's ult he usually gets out of a car and starts chasing me on foot

But comes back to finish the job