I'll have to go back and look at it. I thought the corner/safety had the coverage over the top of Lamb and Dak was trying to stick it in a window between the coverage, expecting Lamb to win the ball. Considering it wasn't the underneath coverage that made the play, but the corner/safety who broke on the ball when Lamb headed toward the back of the end zone, I don't think I'd say that it was blanketed underneath. The pass was there, so it beat the underneath coverage, but Lamb wasn't. If he'd posted up, the defender behind him might have been able to break up the pass or might have tried to go through him and interfered, but it wouldn't have been an interception.
Like us, they weren't on the same page on this. I think the receiver should have posted up where Dak threw the ball. You think Dak should have gone over the top.