Why gform_field_value works for a text field but not for a dropdown?

Both fields are allowed to be populated dynamically and have its parameter name.

This works:

add_filter( "gform_field_value_text_field", "populate_text_field" );
function populate_text_field( $value )
{
   return "Dynamic populated";
}

But this doesn't:

add_filter( "gform_field_value_dropdown_field", "populate_dropdown_field" );
function populate_dropdown_field( $value )
{
	$value = array(
		array( 'text'=>'Foo 1', 'value'=>'foo1', 'isSelected'=>false, 'price'=>'' ),
		array( 'text'=>'Foo 2', 'value'=>'foo2', 'isSelected'=>false, 'price'=>'' ),
		array( 'text'=>'Foo 3', 'value'=>'foo3', 'isSelected'=>true , 'price'=>'' )
	);
   return $value;
}

I know I can use gform_pre_render, and that's how I'm solving this.
But _field_value is much more easy.

I really did a research here in the forum but couldn't find an answer..
Am I missing something?