The issue with Genesis 3 and later is that they gave 2 joints per group on the thighs. Although there are 2 bones there, apparently we only have ONE single map to handle all 3 axes, so the extra Twist bone is useless. Since Genesis 3 and later figures have only a single map per joint, locking is no longer an option. You will be editing the weights for all 3 directions, bending, side-side, and twisting, all in the SAME map. That is, you fix the bend map, and it breaks the side-side and twist, because it's the same map. That's what TriAx was invented to resolve, but now we are back to how it was 20 years ago.
What happened here was that I created a new map on the Thigh Twist bone, and you actually can do that, but the map still becomes tied up to the Thigh Bend map, even if they are separate maps driven by different bones. It couldn't be more confusing than this, but to add to the mess, DS now automatically adds figure JCMs to the outfit, even if it has none. This causes the shapes to change as the legs are posed, which can fool you to think it's because of your weight map, when it's not.
To make it even more fun, DS cannot disable these automatic JCMs. It looks like another tool is needed to stop the JCMs to interfering with your weight maps, but I don't know what it is yet. Conversely, single map per joint has to rely heavily on JCMs to pose properly, but DS has no tools to edit them. TriAx was way easier than this, but we all want to please the gaming companies, by making rigging more compatible with their game engines. Isn't that what we all want?