It’s been a while and it seems; by observing and discussing with Google Staff the direction of Buy On Google is heading, is clearer now. It does not appear Google is building an Amazon style E commerce marketplace but rather is enhancing the Google Shopping marketplace with product consolidation, product ratings etc. in order to drive up conversion rates. The buy on Google is another mean to the goal of getting conversion rates to increase on Mobile at least where Google is running the beta version.
The trend towards a mobile first search market is continuing, Mobile has long overtaken search rates over desktop. Conversion rates on mobile is still stubbornly low and Google needs to increase conversion rates on Mobile. The buy on Google will go a long way to accomplish that.