woocommerce offtopic - Why does wc_get_products($arg) return no products when $arg = 'average_rating' =>

As per documentation the this should return all products with a average rating of 5 but we get no products returned even though we have one product with a rating of 5.

average_rating

Accepts a float: The average rating.

// Get products with all 5-star ratings.
$args = array(
    'average_rating' => 5.0,
);
$products = wc_get_products( $args );