Each Hammer bullet is listed with a minimum required twist for proper terminal performance. The minimum twist rate is much more about terminal performance than ballistic performance. You can get marginally stable bullets to shoot quite well. Problem is they will have a much higher potential for poor performance after impact due to yaw or tumbling. This is true with all bullets not just Hammers. We just happened to be the first ones to beat the terminal performance stability drum. Stability is simply physics. The length of the bullet x the weight of the bullet x the amount of twist. With mono's (at least ours) there really is no max twist. We have yet to find too much. The more twist the better everything works.
I wonder if the OP thought that a bullet listed for a min of 1-12" twist would not work in a 1-10" twist? That is a common mistake. The lower the number the faster the twist. Extra twist is a good thing.