Vertical is vertical, whatever your grip type; either the wrist is or isn't. I don't think that "vertical" is relative. If you play with a 90* turned left hand grip at impact, then it won't be vertical to the ground until very well after impact, unless you're happy with going left of left.
Another way to look at it....
The farther 'up plane' your impact, the more the left wrist is in a 'turned' position. Part of the reason that the back of the left hand should match the angle of approach, not face the target. All of course subject to the rest of the machines alignments and the intended result.
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The farther 'up plane' your impact, the more the left wrist is in a 'turned' position. Part of the reason that the back of the left hand should match the angle of approach, not face the target. All of course subject to the rest of the machines alignments and the intended result.
How about this here for a procedure for Horizontal Hinging with a Turned Left Hand . . .
Club chest high on a horizontal plane with a 10-2-B grip. Now just move the club where it would be through impact with the club vertical to the horizontal plane. Now turn the grip and drop it down on the angled plane. It's kinda liike the thumbpad of the left hand has to stay vertical???