Yeah, that is one absurdly lucky group of chasers. Without a timestamp it's not clear exactly when this video was shot, but they're clearly heading south on Range Line a maximum of a couple minutes before the tornado struck that area. They're passing through 20th and Range Line as the video begins, and if the camera was pointing east instead of west we'd be able to see the Home Depot that was about to be destroyed.What's crazy is that they decided to head east on I-44 and that monster tornado actually ended up taking a turn and went right over I-44. They got very lucky.
Then, as you say, they appear to get on I-44 eastbound and just miss crossing the tornado's path again, since it crossed the interstate (albeit at reduced intensity) about 3 miles east of Range Line and caused damage to some truck stops at an exit there.
I was also struck by the fact that even though there's a 3/4 mile wide EF-5 tornado probably less than a mile to their west, and the camera is pointed in the right direction, there's really nothing that "looks" like a tornado until about 1:20 where you can see the contrast difference between the edge of the funnel and the clouds/rain behind it. It's not till that point that the passengers in the van really seem to spot the tornado either. I wonder if more than a few people simply did not realize what was coming.