Unexpected extra row from jsonb_path_query() with a recursive path

PostgreSQL 12.1, compiled by Visual C++ build 1914, 64-bit
Windows 10

Query:

select jsonb_path_query('{"data": [{"key": "value"}]}', '$.**.key')

Actual output:

jsonb_path_query
------------------
"value"
"value"
(2 rows)

Expected output:

jsonb_path_query
------------------
"value"
(1 row)