suboptimal read isolation when using $in with shard keys

Say I have a collection with a hashed shard key on field "S".

If I send a query such as: db.coll.find({"S": {$in: [...]}}) with[...] being a relative lengthy list (couple of hundred entries). It seems like all entries in there are send to all shards instead of mongos splitting the query appropriately. As a result, each shard has to check for each of the values.