Custom taxonomies to define versions of a product

Taxonomies is not the right approach here, you should use custom fields (post meta) instead this way you can use compare argument of the meta query as <= ex:

$args = array(
        'post_type' => 'product',
        'meta_query' => array(
                array(
                        'key' => '_version',
                        'value' => '1.0',
                        'compare' => '<='
                )
        )
 );
$query = new WP_Query( $args );