After watching this video, it was important to nail down the exact definition of "approach angle," as it applies to off-roading. The Wikipedia definition -- which most off-road bloggers seem to accept -- is:
Approach angle is the maximum angle of a ramp onto which a vehicle can climb from a horizontal plane without interference. It is defined as the angle between the ground and the line drawn between the front tire and the lowest-hanging part of the vehicle at the front overhang.
To give you a little frame of reference, the approach angle of a 2020 4-door Jeep Wrangler Rubicon is 43.9 degrees. The 2021 Ford Raptor in 35-inch tires is a solid 31 degrees. A similarly-clad TRX has an approach angle of 30.2 degrees.
Hummers and Humvees are a little different than most off-road vehicles, however. The civilian version, the Hummer, is available in three models: the H1, H2, and H3. The H3 has a modest approach angle of 37.5 degrees, while the H2 kicks it up to 40.8 degrees. The H1 may seem unstoppable at an outrageous approach angle of 72 degrees, but then this Humvee comes along and climbs a vertical wall.
Now, without scientific instruments, we can't fully confirm that this is a 90-degree climb, but it's probably close enough for the sake of YouTube views.
The driver scoots up gingerly to the wall, even staying within the parking lines, as they prepare to literally climb the wall. Adjustments are made, and soon the Humvee is calmly and obediently standing upright. But, what's really impressive about this video is how calmly and obediently the Humvee returns back to Earth. It sits down with the manners of a well-trained Golden Retriever.
No word on whether this driver was also able to teach this truck to sit and shake in addition to standing up, but hopefully there's video if they did!