I tried that method of Bert's once, and intuitively it makes sense, especially for one-handed play. But if it was that important, I don't think you'd see nearly every snooker player using a very square stance.
I'm not sure how your hand hangs with your arm straight down is that relevant to how it hangs when your shoulder and elbow are in shooting position. For me, standing straight up and holding a cue at its balance point in my right hand naturally, the cue angle inwards at almost a 45º angle. But as soon as I start bending forward from the waist, it starts pointing forwards more, around 25º from straight forward. Then, as I lift my elbow up high in shooting position, the cue naturally straightens up and points straight forward.
Perhaps it's more important to guys with a very upright old-school stance (which makes sense considering when Bert put that video out). I put my chin on the cue, and can play with both a snooker stance or very angled pool stance just fine. I've settled on somewhere in the middle.