Lateral flatten index unsupported

[rogalski]

SQL:

select id, f.value::varchar as v, f.index as i
from (select column1 as id, column2 as col from (values (1, 's1,s2,s3'), (2, 's1,s2'))) as t
, lateral flatten(input => split(t.col, ',')) as f order by id;

Rewritten SQL:

SELECT ID, F.VALUE ->> '$' AS V, F.INDEX AS I FROM (SELECT COLUMN1 AS ID, COLUMN2 AS COL FROM (VALUES (1, 's1,s2,s3'), (2, 's1,s2')) AS _("COLUMN1", "COLUMN2")) AS T, LATERAL UNNEST(CAST(TO_JSON(STR_SPLIT(T.COL, ',')) AS JSON[])) AS F(VALUE) ORDER BY ID;

Error:

snowflake.connector.errors.ProgrammingError: 002043 (02000): None: Binder Error: Table "F" does not have a column named "INDEX"

Version: main

DuckDB docs recommends extra SELECT with generate_subscripts: https://duckdb.org/docs/sql/query_syntax/unnest.html#keeping-track-of-list-entry-positions