I learned this lesson about 15 years ago when I was in a trench carrying moving targets on a stick, 300 yards from the line where guys were shooting 308s. I didn't bring earpro, which was a mistake as it was still pretty loud with those rounds 3' over my head.
The video is also a bit misleading though (not intentionally). My closest neighor is about 400 yards away and if you asked him I bet he would tell you that it is much quieter when I shoot suppressed because he is not in the bullets path. For him, and me, all the BOOOOOOM is gone.
I'd like to see the same test with him 90 degrees to the right (or behind) of the shooter, 25, 100, and 400 yards away.