Not Quite "Absolute" Faith
It looks a bit more daring in the video than it really is. Yes, the right wing, the side the camera is on, was at some times as close as 500' from the snow, at the same time the left wing was quite a bit higher. Also, what is not so easy to see is that this particular mountian is on the westward edge of the range and from most points there is an uninterrupted, or at least relatively uninterrupted, glide path to the valley floor 8,000 - 10,000 feet below. Also, not shown is that there is an airport about 15 miles away. And the RV-12 makes a pretty good glider.
This also brings the weather into play. On this particular day there was alomost no wind. Comparing ground track to true airspeed there was maybe 2 kts from almost due south. It wasn't even enough to create a "burble" over the peak. Most other days the wind would be far too strong, unstable, and bumpy to even think of getting that close, not to mention the strong down drafts that can form on the back side.