Two consecutive chunks (blue, amber) are each perfectly fine, but they disagree at the hand-off. Switch between them naively (hard cut, or a blind average) and the executed action jumps — the lower panel shows a catastrophic acceleration spike, the kind that snaps a wrist or trips a safety stop. Widen the inpaint blend (RTC's trick: condition the new chunk on the committed one) and the executed trajectory stays smooth, acceleration bounded. Matching distributions across the boundary, not points, is what keeps it physical.