Registering Field for Acf Block Does Not Work

I created a block with acf_register_block_type which shows the block in editor which is complete fine. I did that this way,

//custom block with acf
function mab_register_acf_block_types() {
    acf_register_block_type( [
        'name'            => 'blockquote',
        'title'           => __( 'Blockquote' ),
        'description'     => __( 'My blockquote block.' ),
        'render_template' => dirname( __file__ ) . '/blocks/blockquote/blockquote.php',
        'category'        => 'formatting',
        'icon'            => 'format-quote',
    ] );
}

if ( function_exists( 'acf_register_block_type' ) ) {
    add_action( 'acf/init', 'mab_register_acf_block_types' );
}

But I wanted to register the field for this block which actually does not work. The registration of field done this way

add_action('acf/init', function () {
        if( function_exists('acf_add_local_field_group') ):
    
            acf_add_local_field_group(array (
                'key' => 'group_1',
                'title' => 'My Group',
                'fields' => array (
                    array (
                        'key' => 'field_1',
                        'label' => 'Sub Title',
                        'name' => 'sub_title',
                        'type' => 'text',
                        'prefix' => '',
                        'instructions' => '',
                        'required' => 0,
                        'conditional_logic' => 0,
                        'wrapper' => array (
                            'width' => '',
                            'class' => '',
                            'id' => '',
                        ),
                        'default_value' => '',
                        'placeholder' => '',
                        'prepend' => '',
                        'append' => '',
                        'maxlength' => '',
                        'readonly' => 0,
                        'disabled' => 0,
                    )
                ),
                'location' => array (
                    array (
                        array (
                            'param' => 'block',
                            'operator' => '==',
                            'value' => 'blockquote',
                        ),
                    ),
                ),
                'menu_order' => 0,
                'position' => 'normal',
                'style' => 'default',
                'label_placement' => 'top',
                'instruction_placement' => 'label',
                'hide_on_screen' => '',
            ));
    
        endif;
    });

If I set the location to something else like post_type , it is okay, which means the code for registering the field is working for post_type but if I set the location to block == 'blockquote', it's not working. Is there anything wrong I am doing or is it the bug of acf ?