做补语的形容词可以做插入句吗

The non-native speakers, it turns out, speak more purposefully andcarefully, typical of someone speaking a second or third language.

请问这里的typical of someone speaking a second or thirdlanguage是做主语The non-native speakers的补语对吗？

可以单独做插入句用吗？

可以视为前面整个主语从句的补语，而非主语的补语。