"supportsAggregatePushdown": does not work correctly on sharded Mongo Cluster

[tfold]

Drill 1.2.1
Mongo 4.4
Mongodb Config: 2 shards/3 replicas
Mongos on port 27017

DrillBit:

{
"type": "DB",
"connection": "mongodb://mongo01:27017,mongo02:27017/?readPreference=secondaryPreferred",
"pluginOptimizations": {
"supportsProjectPushdown": true,
"supportsFilterPushdown": true,
"supportsAggregatePushdown": true,
"supportsSortPushdown": true,
"supportsUnionPushdown": true,
"supportsLimitPushdown": true
},
"batchSize": 100,
"enabled": true,
"authMode": "SHARED_USER"

Running a count(*) on the above drill only returns the # of records on one shard. Changing "supportsAggregatePushdown": to false reports the correct count from both shards.

Same query from mongo shell reports total across both shards.

Since we are querying mongos from drill, the count should include records from both shards, but for some reason it only reports a count on the shard that it is talking to.