unknown column with aggregation inside derived table

[systay]

For the query:

select u.id, u.name, t.num_segments from (select id, count(*) as num_segments from user group by 1 order by 2 desc limit 20) t join unsharded u on u.id = t.id

We produce the following plan:

{
  "OperatorType": "Join",
  "Variant": "Join",
  "JoinColumnIndexes": "R:0,R:1,L:0",
  "JoinVars": {
    "t_id": 1
  },
  "TableName": "`user`_unsharded",
  "Inputs": [
    {
      "OperatorType": "Limit",
      "Count": "20",
      "Inputs": [
        {
          "OperatorType": "Route",
          "Variant": "Scatter",
          "Keyspace": {
            "Name": "user",
            "Sharded": true
          },
          "FieldQuery": "select t.num_segments, t.id, count(*) from `user` where 1 != 1 group by id",
          "OrderBy": "2 DESC",
          "Query": "select t.num_segments, t.id, count(*) from `user` group by id order by count(*) desc limit 20",
          "Table": "`user`"
        }
      ]
    },
    {
      "OperatorType": "Route",
      "Variant": "Unsharded",
      "Keyspace": {
        "Name": "main",
        "Sharded": false
      },
      "FieldQuery": "select u.id, u.`name` from unsharded as u where 1 != 1",
      "Query": "select u.id, u.`name` from unsharded as u where u.id = :t_id",
      "Table": "unsharded"
    }
  ]
}

The issue is with this line:

select t.num_segments, t.id, count(*) from `user` group by id order by count(*) desc limit 20

The derived table t doesn't exist, so this query errors out with:

target: xyz.-24.replica: vttablet: rpc error: code = NotFound desc = Unknown column 't.num_segments' in 'field list' (errno 1054)