During a newborn screening program in Delhi, two infants with developmental dysplasia of the hip are identified. Infant A has a positive Ortolani test with a palpable clunk and a normal abduction angle. Infant B has a negative Ortolani test but restricted abduction (<50°) and a positive Barlow test. Which clinical finding best distinguishes Infant A (acute/recent dislocation) from Infant B (chronic/neglected dislocation)?