getInventoryItems Response Different from getInventoryItem for Same Item

Hello,

We are running into a weird issue where the response for the same item is different between getInventoryItems and getInventoryItem.

When using getInventoryItem with the item SKU, we receive the expected JSON response back:

{
  "sku": "sku",
  "locale": "en_US",
  "product": {
    "title": "title",
    "aspects": {
      ...list of aspects
    },
    "description": "description",
    "brand": "brand",
    "mpn": "mpn",
    "imageUrls": [
      list of images
    ]
  },
  "condition": "NEW",
  "packageWeightAndSize": {
    "dimensions": {
      "width": 9,
      "length": 12,
      "height": 1,
      "unit": "INCH"
    },
    "packageType": "LARGE_ENVELOPE",
    "weight": {
      "value": 8,
      "unit": "OUNCE"
    },
    "shippingIrregular": false
  },
  "availability": {
    "shipToLocationAvailability": {
      "availabilityDistributions": [
        {
          "merchantLocationKey": "X",
          "fulfillmentTime": {
            "value": 2,
            "unit": "BUSINESS_DAY"
          },
          "quantity": 0
        }
      ],
      "quantity": 0,
      "allocationByFormat": {
        "auction": 0,
        "fixedPrice": 0
      }
    }
  }
}

However, the response for that same item under the getInventoryItems call is much more simple:

    {
      "sku": "sku",
      "condition": "NEW",
      "packageWeightAndSize": {
        "dimensions": {
          "width": 9,
          "length": 12,
          "height": 1,
          "unit": "INCH"
        },
        "weight": {
          "value": 8,
          "unit": "OUNCE"
        }
      },
      "availability": {
        "pickupAtLocationAvailability": [
          {
            "merchantLocationKey": "X"
          }
        ],
        "shipToLocationAvailability": {
          "quantity": 0
        }
      }
    }

As you can see, the JSON for that SKU in the getInventoryItems response is missing "product" key.

To add to it, it only happens for this specific item. There's no difference between this and other items that have been created via the API.

We need the JSON for that SKU in the getInventoryItems response to match the getInventoryItem response.

Any assistance from other sellers / eBay will be appreciated.