Power BI Report builder query parameters sends null to database

I'm calling a proceedure in MariaDB. I noticed that when the query is parameterized, it doesn't send the values I added to the parameters. So I created this sample proceedure where it returns the values it received back.

CREATE DEFINER=`root`@`localhost` PROCEDURE `reporting_db`.`proc_Hello`(
    IN `P_StartDate` DATE,
    IN `P_EndDate` DATE
)

DETERMINISTIC
begin
    SELECT `P_StartDate`, `P_EndDate`;
END

When I hardcode the start date and the end date, I get the result back correctly. (Here, start date parameter has a default value of 2020-01-01)

When parameterized however, query sends null instead.

For parameterized start date, I get back null.

I tried changing start date and end date to varchar(50) in the proceedure but result is the same. What is wrong here?