The behavior did change slightly between 7.x and 8.5. here's the note
from the relase notes for 8.5
Allowing Users to Toggle Between the Touchtone and Voice-Recognition Conversations
In Cisco Unity Connection 8.0, users were able to press 9 to switch from the voice-recognition conversation to the touchtone conversation. In Connection 8.5, that functionality has been enhanced. Now, when the user presses 9 while in the main menu of the conversation, the key press functions as a toggle between the voice-recognition and touchtone conversations. If users are assigned to the voice-recognition conversation and press 9 while in the main menu, they are switched to the touchtone conversation, and vice versa.