This is unfortunate that there is no longer an option to retrieve the zero metrics rows.
Here is an example of a real-world situation. When looking at bid_adjustments broken down by household income segments, segmented however one wishes (Date + maybe device, etc...) , if the metrics for that segment are all 0 it won't return the result, but you can see the result in the UI. This particular segment has a bid_adjustmnet of say -59%, but that becomes invisible in API reports, leading to discrepancies between API and UI displayed information and leads to a lack of trust from our clients of the API data when compared to the UI. This is frustrating to say the least. This was not an issue in adwords, as there was an explicit option to include or exclude zero-metric rows in the API reports.
The left side of the screenshot is the API report, Right side is the UI downloaded report all filtered to the same campaign, ad group, and date. Ordered by impressions for easy comparison. As you can see, the bottom two rows on the right (from the UI) do not appear on the left (from the API) You can clearly see how not being able to provide rows with zero metrics results, fails to provide needful and valuable information about bid_adjustments. If i used the API only, then i would not see that the other two segments are currently -59% and -22% for bid_adjustments.
