StorageStatistics() returns invalid (0) value for avgItemSize and avgPageSize for collection with small number of documents

insert into default.scope1.coll1 values("key1", {"c1":1, "c2":1});

insert into default.scope1.coll1 values("key2", {"c1":2, "c2":2});

insert into default.scope1.coll1 values("key3", {"c1":3, "c2":3});

create index idx1 on default.scope1.coll1(c1,c2);

update statistics for default.scope1.coll1 index all;

select * from system:dictionary where `bucket` = "default";

    "results": [

    {

        "dictionary": {

            "avgDocKeySize": 4,

            "avgDocSize": 30426,

            "bucket": "default",

            "distributionKeys": [

                "c2",

                "c1"

            ],

            "docCount": 3,

            "indexes": [

                {

                    "indexId": "eb63e08cd3935a39",

                    "indexName": "idx1",

                    "indexStats": [

                        {

                            "avgItemSize": 0,

                            "avgPageSize": 0,

                            "numItems": 3,

                            "numPages": 1,

                            "resRatio": 1

                        }

                    ]

                }

            ],

            "keyspace": "coll1",

            "namespace": "default",

            "scope": "scope1"

        }

    }

    ],