but I think it's Cover 3 with 4 under. But there are two Cowboys bunched together so it looks odd. Gurley is not open, but there are 2 guys open elsewhere
But, Goff knows that it's a zone and there is a hole after the short zones and before the deep zones, and knows those two defenders covering Gurley will drop him. In real time it doesn't look like they drop Gurley, but they do, their eyes are in backfield, and Goff knows it zone due to that, or he rds them in other words and he knows Gurley will blow past them (even is leavin')
Goff chould have gone for the TE in middle, would have been a good gain, but he took a shot and it paid off with TD