a row is not inserted in nested INSERT ON CONFLICT

Hi,

On versions 15.2 and 16.4:

    create table a (i int, j int, k int, t timestamp default (clock_timestamp()), unique (i));
    insert into a values (1, 1), (2, 2), (3, 3);
    with w(i) as (
        insert into a values (1, 100), (2, 200), (3, 300) on conflict (i) do update set i = excluded.i + 10, t =
clock_timestamp(),k = 0 returning i
 
    ) insert into a values (1, 10), (2, 20) on conflict (i) do update set i = (select (i - 10) from w order by i desc
limit1), t = clock_timestamp(), k = 1;
 
    table a;

gives

    INSERT 0 1

and

     i  | j  | k |             t
    ----+----+---+----------------------------
     11 |  1 | 0 | 2024-08-12 15:13:56.209344
     12 |  2 | 0 | 2024-08-12 15:13:56.209361
     13 |  3 | 0 | 2024-08-12 15:13:56.209368
      2 | 20 |   | 2024-08-12 15:13:56.209375
    (4 rows)

The order of executor events from what I can tell is

- start (1, 10)
  - start (1, 100)
  - end (1, 100)
  - start (2, 200)
  - end (2, 200)
  - start (3, 300)
  - end (3, 300)
- end (1, 10)
- start (2, 20)
- end (2, 20)

I find it unusual that the (1, 10) insert seems to be ignored.

Jason