Index not being used, if parameter binding is used in combination with UNION in subquery/view

Reproducer query:

SELECT *

FROM (

    SELECT * FROM my_table

    UNION ALL

    SELECT * FROM my_table

) q

WHERE q.column_with_index = ?;

I am using PHP to execute this query. Everything works fine when using PDO's emulated parameter bindings. The execution is fast and "EXPLAIN SELECT ..." reveals that the index on column "column_with_index" is being used.

Things change when I set "PDO::ATTR_EMULATE_PREPARES" to "false": When using MariaDB's native parameter binding protocol, the index is not being used.

This behavior changes again, depending on the exact parameter binding protocol + charset + database API combination.

I've posted my question to StackOverflow and somebody suspected this to be a bug in MariaDB.
The post can be found here: https://stackoverflow.com/q/79245146/1529133

I've also prepared a reproducer here:
https://phpize.online/sql/mariadb115/a1c61a1321ba2adfc689bd9e87e75ad9/php/php82/c602157f683d216f384ec3e56833df9b/