Google Voice is not a standalone app. It is a service, just like Gmail, Calendar, Contacts, Docs, etc. All Google services are accessed via a Google account (a Gmail address and password).
So, if you want to use 2SV on your Google
account, then sure, you can do that. However, OBiTALK devices are not signing into your full Google account. You perform a one-time authorization to allow the OBiTALK device to access the Google Voice service on your Google account. When you do this, you are already signed in to your Google account. The OBiTALK procedure exchanges OAUTH secure tokens that are specific to that device.
Learn more about Google's 2SV here:
https://support.google.com/accounts/answer/185839?hl=en&ref_topic=2954345