This paper examines two Mandarin semantic operators, additive YE and distributive DOU, in the end state knowledge of two groups of Cantonese-speaking learners who differ in the age of acquisition and input frequency and quality. The results suggest that although the end state grammar of YE and DOU of the Hong Kong and Guangzhou learners diverge from native representations, the Guangzhou learners shows less divergence (i.e., more convergence). We suggest that age of acquisition from before three years old with the Guangzhou learners may positively impact the chances of convergence with native-like representations. Comparing the Hong Kong and Guangzhou learners' end state grammar of YE and DOU, we argue that there are critical period effects on the acquisition of phrasal semantic properties at the semantic-pragmatic interface. The current study therefore supports the Interface Hypothesis in the sense that even sequential bilinguals and early L2 learners may not attain native-like competence in their acquisition of linguistic properties at the semantic-pragmatic interface.