“Invalid parameter(s): attributes” issue in context of “blocks.registerBlockType” filter

In what way is the Tag Cloud block different?

That block is a dynamic block, which uses a live rendering using ServerSideRender, and the documentation stated that “If you pass attributes to ServerSideRender, the block must also be registered and have its attributes defined in PHP“, therefore, custom attributes for the block must be defined in PHP as well and not just JavaScript.

To fix the issue, you can use the register_block_type_args filter to add the blockAnimationClass attribute. E.g.

add_filter( 'register_block_type_args', 'my_add_custom_block_type_attributes' );
function my_add_custom_block_type_attributes( $args ) {
    $args['attributes']['blockAnimationClass'] = array(
        'type'    => 'string',
        'default' => '',
    );

    return $args;
}