Google probably has to do a whole communication campaign to help us understand the differences between its various mobile payment apps and platforms because it's getting kind of confusing. A recent apk teardown had also indicated new incoming features for the Google Contacts app, and this seems to have arrived, at least for a user in Canada. This seems to be the same feature that they introduced to Android Messages which enabled peer to peer payment services on the messaging app.
Last year, Google had added the ability to transfer money to Android Messages through Google Wallet.
The company says in a press note: "Starting today, Google Duo users can send a video message to their friend or family member, who will receive it in the Duo app". After selecting the desired one, a Google Pay dialog box will open prompting you to enter the amount to send.
Furthermore, a "Knock Knock" feature lets users see a live preview of the caller before answering. Although Google has yet to make any announcements, it looks like some Android users discovered the new feature is available and ready to use. But this may also be because it is a server-side change and so Google has not yet finished the full update. Tapping on that will prompt you to send money to which number or email.