A Reddit user spotted the change when initiating the call recently. Also, Google launched a help page that outlines how the upgrade works, including the caveat that P2P connections will reveal your IP address.
A Google representative confirmed to Venturebeat that Google will roll out the change across all platforms: Android, iOS, and the web. So you may see such an improvement next time you use Hangouts to make a voice call.
Why this matters: This move should help Hangouts with better call quality, which I’ve found to often be a subpar and frustrating experience. Google notes this feature will kick in when possible, so don’t expect to see it every single time.