Disabled SAMPLE MODE in Aggregations does not work for a high number of documents collection.

Steps to reproduce:

1. In Aggregations page, disable the SAMPLE MODE.
2. Use $group with below query. This will result in the count of the documents to this stage.

{
    _id : null,
    count : {
       $sum : 1
    }
}

3. The result displays the number of LIMIT configured or 100000 by default.

My hypothesis is the number of documents plays a part in the issue and have asked the customer to test with other collections. Please see the below table that describes the relation of this issue with the number of documents in a collection.
Note, I do not see any document note that the SAMPLING will be force used if the number of documents exceeds X number.