X++ Method parameters actually pass by value or reference?

Good morning everyone. This is just a short note. I've seen a code which update/change the value of a parameter variable.(see below) This make me very confuse because as far as I knew normally X++ parameters are passed by value.

void test(EcoResProductMaster _EcoResProductMaster = null)

{

    ;

    EcoResProductMaster.data(_EcoResProductMaster);

    this.aaa();

    this.bbb();

    this.ccc();

    _EcoResProductMaster.data(EcoResProductMaster);

} 

I googled and then I found the following useful link.

https://gatesasbait.wordpress.com/2007/12/05/parameter-passing-in-dynamics-ax

So there are two base types in X++ which are passed by reference. They are record and class.

String	Assigned and passed by VALUE
Integer	Assigned and passed by VALUE
Real	Assigned and passed by VALUE
Date	Assigned and passed by VALUE
Enum	Assigned and passed by VALUE
Container	Assigned and passed by VALUE
Record	Assigned and passed by REFERENCE
Class instance (any object instanciated with ‘new()‘)	Assigned and passed by REFERENCE
AnyType	Assigned and passed by VALUE, even when holding a Record or Class instance
Guid	Assigned and passed by VALUE
Int64	Assigned and passed by VALUE

Hope that helps, enjoy your day.