This was the first time I've heard of it as it was considered classified by those in channel at the time. I've been told this is the 2nd of 3 times it was attempted and each time they were able to recreate it. I believe you just need the right hill/speed.
The 1st time this happened (again before the footage above) they both jumped out of the V3S and were invisible (to each other) before relog. So this time they wanted to see the extent of this exploit and record it in order to submit a report.