sharded_agg_helpers::attachCursorToPipeline can be run from both the router and shard (mongos and mongod). However, thus function uses the ShardingState service-context decoration, which should only be present on mongod, to get the 'local' shardID for use in an optimization.
This is innocuous for now because the ShardingState is never initialized on mongos and the 'default' shardId isn't targeted. But we should remove the use of this shard-role code from code that can run under the router role. Removing ShardingSTate from mongos is tracked via SERVER-81023