The user has uploaded screenshots on Nokia Forum and you can see the user interface during the call. As you can note, the record button can be accessed while swiping from right to left over the call screen on a dual SIM device. In all likelihood, the feature will roll out to all Google Pixel phones and Android One devices.
Some of the users pointed out that the person is using US VPN and thus the Call Recording feature is showing up. However, others chimed in and claimed that the feature is live for them as well. It is worth noting that the feature will be available only on Pixel and other phones running near-stock Android setup.
At this point in time, there is no way you can force add the feature on your phone. All you can do is wait for Google to roll out the Call Recording feature. Also, make sure that you download and use the latest beta. There are good chances that the feature might be available on your phone as well.
Call Recording feature seems like an amazing feature for Google Phone. However, it is quite likely that Google might end up in a legal quagmire. Telephone recording laws differ from one place to another and typically require consent from either one or both the parties.[via XDADevelopers]