GA Reporting API session and product correlation

I ran into this issue a few months ago and nobody responded. It has come up again and I'm wondering if anyone knows why it doesn't work. Here's the original question:

Correlating certain metrics with Sessions and Products in Google Analytics API v4

The issue is correlating products to session/page information. If you setup an api query with a session variable (e.g. ga:sessions) or a page variable (e.g. ga:pageviews) and try to correlate it to a product dimension (e.g. ga:productSku), it will always give an empty data set.

I'm wondering A) why this data can't be correlated, B) why both google's dimension/metric explorer as well as their query explorer allow these combinations, but never return data, and C) is there a way around it?

I've tried this on about 10 clients that all have lots of product data and the result is always the same.

Edit: Adding example report json for ease of replication:

{
    'reportRequests': [
    {
      'viewId': VIEW_ID,
      'dateRanges': [{'startDate': '7daysAgo', 'endDate': 'today'}],
      'metrics': [{'expression': 'ga:sessions'}],
      'dimensions': [{'name':'ga:productSku'}],
      'pageSize': 10000
    }]
  }