One other random observation that occurred to me recently and that I chatted with Ryan about yesterday while our training overlapped a bit.
Background: I was introduced almost simultaneously to Starting Strength, Crossfit, and Olympic Lifting just over 9 years ago, in Jan or Feb or 2008. I had never heard of SS before; I'd vaguely heard of Crossfit; and I had known of olympic lifting for years, but never actually did it at all. Throughout 2008, 2009, and 2010, I read a lot of different coaches' takes on things and tried a lot of different ways of doing things. No one can claim to have tried everything, but I tried an awful lot. As I've written about several times, I DID start squatting below parallel at that point, but never did a single low bar rep till 2011. Since 2012, I've been more focused on our community here and learning and engaging with SSCs and others who share our basic outlook. I still read and look at other sources, but with a more skeptical eye than before.
But, one of the things I never did much experimenting with until more recently was adjusting my low bar squat grip. I always felt very stable and secure with the standard SS grip, and aside from two bouts of elbow tendinitis that went away after a few weeks of rest, never had any problems with it or reason to experiment with something different.
Starting in 2015, I think, I did occasionally use a thumbs around grip for low bar, but that was only occasional. Maybe two dozen times, total.
Recently I started having more severe and almost cripplingly bad right elbow issues that I could trace to my squat and the grip. So I've been playing with different grips and using the thumbs around grip a lot, and consistently, while experimenting with different widths and elbow positions.
It has been while doing so, an insight occurred to me that I thought I'd share for others' consideration.
In general in the PL world, some of the cues you hear a lot are "bend the bar across your back" and "drive your elbows forward at the bottom and as you start to drive up." SS doesn't use either of those cues, and in fact, we generally want a lifter's elbows to remain stably and consistently up throughout the lift. Not excessively up - see Jordan's article for more on this - but up enough to create a stable rear delt shelf and a lifted chest and tight thoracic area.
As one of the few things I'd not really experimented much with, I never understood those cues. They seemed counterproductive (elbows down) or unnecessary (bend the bar across your back). And certainly never understood the sometime scorn I would see by other lifters or internet lifting people for those who squatted with elbows up, as if they were committing a huge blatant and obvious squat error, and as if these cues were crucial to the mechanics and performance of the squat itself.
After a few months of consistent thumbs around , elbows more down squatting, I think I understand.
Holding the bar with the thumbs around and elbows down means a highly extended wrist. The hands, therefore, are not in position to exert downward force and leverage on the bar and prevent it from rolling up the back as a lifter leans over into a low bar squat. The hands ARE in this position in a thumbs over/elbows up grip, and just the tiniest bit of effort and focus is needed to use that position advantageously to "pin" the bar to the lifter's back. But with the elbows down, that leveraged position is simply not possible. And while the extended wrists (probably wrapped) bear the brunt of the downward force and weight of the bar to prevent it from rolling down, there's nothing to prevent it from rolling up.
Therefore, the cue "bend the bar (down) across your back" is needed to cue the lifter to pull the bar down into place to prevent it from rolling UP while the lifter leans over. While not in an advantageous position of leverage for the hands and arms, if you pull down, you can create this effect and keep the bar more stable than if you don't pull down.
It could be that I'm simply not as experienced and good at it yet, but to date, I still feel like the bar is less stable and moves more on my back with this grip than with the standard SS grip. And I am therefore subconsciously reluctant to lean over as much as I should, and consequently have more knee slide. But that's my own issue. Back to the topic at hand.
The "drive the elbows forward" deal, is, I think, related. Elbows up, again, makes it easier to prevent the bar from sliding down, but if thumbs are around and wrists back, with the elbows up, the hands have even less leverage to "pull down" on the bar and keep it in place from sliding up. And right at the bottom and out of the hole is when you're going to be most leaned over in the squat, especially if there's that slight back angle change as the direction reverses that we usually see at heavy weights. So it's a reminder to keep your arms in a position where "bending the bar down across the back" to keep it stable and prevent it from sliding up, is possible.
If I am correct, the problem isn't these cues. They're perfectly understandable and acceptable for someone using this grip. It's that the cues are an artifact of the grip, not at all inherent or meaningful to the mechanics of the squat itself. But the thumbs around/wrists bent grip has been the standard for the vast majority of lifters for so long, that the community at large has forgotten the origin of these cues as side effects/consequences of the grip, rather than anything inherent in the mechanics or performance of the squat itself.
That's my take based on my experiences thus far. Maybe it's not original, but I've never heard or seen it before and have read PL stuff that, at least, seems as if they think the elbows down and bend the bar thing are inherent squat mechanics issues rather than artifacts of the grip.