Japanese Word Handler move based on character type, while Word Divider move based on word recognition.
Using Word Handler
Using Japanese Word Handler
While Word Divider divides 拡張機能 into 拡張 and 機能, and 使うと into 使う and と, we can see that the Japanese Word Handler treats 拡張機能 as 拡張機能 and 使うと as 使 and と.
Extension Settings
wordDivider.locale: The locale to use for word divider
auto: Use VS Code's configured display language (default)