Its easyIt's a semantics issue... but yeah I guess grid-export is "possible".
But the terms of the agreement I saw meant I could not voluntarily put energy back when I wanted. I'd have to allow PG&E to take it from me when they felt it was necessary.
I think most people who think of "exporting to the grid" think of exporting a certain kWh that they assign at a time they want to export it. So I don't think what Sunrun/PG&E are supporting is technically in line with what you or I would find valuable as a grid-exporting ability.
And no, I still don't know how to grid charge during off peak... that's probably the feature we all want so we could charge up during 1am if the next day had a lot of clouds in the forecast.