Unfortunately, it appears that walking 128 steps no longer works, at least in Suicune's area
EDIT: It's definitely doing something with no syncher, but with a syncher my results may be inconsistent
EDIT2: I see what's happening. With a seed of F30004C2, no syncher, and 3 roamers out, I get a starting frame of 4. With a syncher, playing from the same save state, I get a starting frame of 5. With a syncher, walking 256 steps, I get a frame of 15. Without, I get 14.
EDIT3: Maybe my calculations were off, as now I am getting a frame of 15 after walking 256 steps with 5 pokes in my party both with and without a syncher. However, in previous testing (with different seeds), I was getting an offset of 4 with a syncher, and either 4 or 5 without. This is weird.