You still get leverage with shanks, no matter how straight or curved they are. Those bits look identical to me. Just because a company doesn't label it a tom thumb doesn't mean it isn't similar or can have the same issues. Take this bit for example: Western NP Snaffle Training Bit - Horse.com Looks pretty much like the exact same bit you first posted about. Yet it's not called a tom thumb.
There's a lot that goes into the leverage of a curb bit, the angles of the shanks as well as the ratio above & below the bit. The issue with tom thumbs isn't their shanks so much as the fact you're pairing snaffle + curb. You're getting dual action from the bit when you tug on it. Not only is it breaking in the center & jacking the horse in the mouth, but it's also adding leverage & pressure at the same time. Now I'm no bit expert so I'm sure someone will come along & correct me. Whether it's labeled tom thumb or not doesn't "safe" or "not safe." Snaffle + shanks should never be paired together. That's the biggest cardinal rule I've learned here. Not to say there aren't some horses that go well in them or do actually like tom thumbs. It would just never be my first pick.
The only thing that makes the bit pictured better than the original Tom Thumb bit is the fact that the shanks are slightly swept back. The swept back shanks will change the balance of the bit allowing the horse the find 'neutral' in a little more natural head position as opposed to the straight shanked Tom Thumb where 'neutral' is when the bit is vertical and on a loose rein meaning the horses face would always have to on the vertical to get complete relief from it. Posted via Mobile Device