In DV360 reporting, if no specific attribution model is manually selected for a data set, which model is used as the default?

In standard Display & Video 360 reporting, the default attribution setting is the Biddable Conversions model when no attribution model is explicitly selected. Google states that if no attribution model is selected, the report uses the biddable conversion model by default. This model is based on the Primary attribution model and respects the Floodlight activity selections applied at the line item level. That is why the correct choice is the primary bidding model rather than another reporting-only attribution rule. Google Help