Problem Statement/Rationale

$let aggregation stage when used with $avg (Array) produces incorrect result

Please be sure to attach relevant logs with any sensitive data redacted.
How to retrieve logs for: Compass; Shell

Steps to Reproduce

db.products.insertMany([
    {
      _id: 1,
      name: "UltraHD TV 55''",
      price: 1200.00,
      rating: [5, 4, 5, 3, 4],
      stocks:

{         "New York": 20,         "Los Angeles": 15,         "Chicago": 10,         "Houston": 5,         "Phoenix": 8       }

    },
    {
      _id: 2,
      name: "Smartwatch 4",
      price: 299.99,
      rating: [4, 5, 4, 4, 5],
      stocks:

{         "New York": 25,         "Los Angeles": 20,         "Chicago": 15,         "Houston": 10,         "Phoenix": 12       }

    },
    {
      _id: 3,
      name: "Wireless Earbuds",
      price: 129.99,
      rating: [4, 3, 4, 5, 4],
      stocks:

{         "New York": 30,         "Los Angeles": 25,         "Chicago": 20,         "Houston": 15,         "Phoenix": 18       }

    },
    {
      _id: 4,
      name: "Gaming Laptop",
      price: 1500.00,
      rating: [5, 5, 5, 4, 5],
      stocks:

{         "New York": 10,         "Los Angeles": 8,         "Chicago": 12,         "Houston": 5,         "Phoenix": 4       }

    },
    {
      _id: 5,
      name: "Tablet 8''",
      price: 450.00,
      rating: [4, 4, 3, 4, 4],
      stocks:

{         "New York": 40,         "Los Angeles": 35,         "Chicago": 30,         "Houston": 25,         "Phoenix": 20       }

    }
  ]);

db.products.aggregate([
  {
    '$project': {
      name: 1,
      updateNeeded: {
        '$let': {
          vars: {
            avgRating:

{               '$avg': '$ratings'             }

          },
          in:

{             '$lt': [               '$$avgRating',               3             ]           }

        }
      }
    }
  },
  {
    '$sort':

{       _id: 1     }

  }
])

Output - 
[
 

{     _id: 1,     name: "UltraHD TV 55''",     updateNeeded: true   }

,
 

{     _id: 2,     name: 'Smartwatch 4',     updateNeeded: true   }

,
 

{     _id: 3,     name: 'Wireless Earbuds',     updateNeeded: true   }

,
 

{     _id: 4,     name: 'Gaming Laptop',     updateNeeded: true   }

,
 

{     _id: 5,     name: "Tablet 8''",     updateNeeded: true   }

]

Expected Results

All documents must have updateNeeded as 'false'

Actual Results

updateNeeded is 'true' for all documents

Additional Notes

Any additional information that may be useful to include.