They move to a more complex system as defined by the five levels. Longitudinal analysis of normally developing children from various language backgrounds fits this description as well. All segments are stops, nasals, glides, or vowels. Default principles 1. All consonants are stops.
All obstruents are voiceless unaspirated.
All sonorants are nasals. Possibly it is compatible with the other feature geometry, but there is no independent motivation for it. But this requires achieving some control over the coordination of gestures in these units. We don't even need to assume that child can at this stage reliably control the difference among stops, nasals, and glides. Likewise, velum gesture is not reliably coordinated with oral constriction gesture.