Sorry for delay!
To whoever may need this kind of info, especially who purchased and use Google Product Feed, I solved that with the following snippet in functions.php:
function lw_woocommerce_gpf_description( $description, $ID ) {
$product_description = strip_tags ( sf_get_post_meta($ID, 'sf_product_short_description', true) );
if ( $product_description ) {
$desc = $product_description;
} else {
$desc = get_the_title( $ID );
}
return $desc;
}
add_filter( 'woocommerce_gpf_description', 'lw_woocommerce_gpf_description', 10, 2 );