@yenching Thanks for the question. Can you please share the document/sample that you are trying. The wake on voice feature enables the user to activate and query a speech recognition engine from various device states by saying a certain keyword.
Yes by default it will go to global dialog, Please raise an issue in the following repo.
Custom Keyword activation in speech services.
https://learn.microsoft.com/en-us/azure/cognitive-services/speech-service/tutorial-voice-enable-your-bot-speech-sdk#add-custom-keyword-activation