Discovery and Engagement API Data missing impressions for specific sources

I've set up the Discovery and Engagement Report via the API to create daily reports. I'm using the Standard report so it includes all of the data and doesn't remove any as per the privacy policy.

It's providing impression data for the App Store Search and App Store Browse source types but it's missing impression data for the others (web referrer and app referrer) - this data is available in the dashboard.

Also, the impression data that I do have does not align with the dashboard, I thought using the standard report would mean all of the data would get provided.

The product page view data is correctly being provided in the data for each of the source types.

Any ideas why it's missing?

Discovery and Engagement API Data missing impressions for specific sources
 
 
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