A potential 'Look and Talk' feature has been found by 9to5Google in the latest Google app beta APK files. The reported tool would enable the Nest Hub Max to use its camera to determine if you were looking at the screen and trigger the Google Assistant from up to 5 ft (~1.5 m) away.
https://www.notebookcheck.net/A-Look-and-Talk-feature-could-be-coming-to-the-Google-Nest-Hub-Max.613763.0.html