What is the expect action when using $in to query on an array

[ShongSu]

Hi,
I have such data in my db:

{ "_id": 1, "name": "aaa", "dp": ['dp1'] }, 
 { "_id": 2, "name": "bbb", "dp": ['dp2'] },
{ "_id": 3, "name": "ccc", "dp": ['dp2','dp1'] },
{ "_id": 4, "name": "ddd", "dp": ['dp1', 'dp2','dp3'] }, 
{ "_id": 5, "name": "eee", "dp": ['dp1','dp3'] },
{ "_id": 6, "name": "fff", "dp": ['dp2','dp3'] }

Here I am supposed to get dp' array contains dp1 or dp2 or both.

This is my query code:

collection.find({ dp: { $in: ['dp1','dp2'] }}).toArray(function(err, documents){
    console.log(documents)
});

When I run this test on Mongo v3.4.16 and v3.6.6, the results are as we expected.

{"_id":1,"name":"aaa","dp":["dp1"]}
{"_id":2,"name":"bbb","dp":["dp2"]}
{"_id":3,"name":"ccc","dp":["dp2","dp1"]}
{"_id":4,"name":"ddd","dp":["dp1","dp2","dp3"]}
{"_id":5,"name":"eee","dp":["dp1","dp3"]}
{"_id":6,"name":"fff","dp":["dp2","dp3"]}

But when I run the same query in Tingo, what I got is

[ { _id: 1, name: 'aaa', dp: [ 'dp1' ] },
  { _id: 2, name: 'bbb', dp: [ 'dp2' ] } ]

I tried on apiLevel both v1.6 and v2.0, they give me same result.

I am not able to find documentation of Mango v1.6 or v2.0 on their official website, so I am not sure if the $in has different functionality in earlier version or it is a bug in Tingo?