A short description of a product is inserted in the meta description

Hello @theevoq,

Thank you for contacting the support.

If you want to apply the Global Description only to the products, please replace the filter that you are using with this one:

add_action( 'rank_math/frontend/description', function( $generated ) {
if ( ! is_product() ) {
return $generated;
}

global $post;
$desc = RankMath\Helper::get_settings( "titles.pt_product_description" );
$desc = RankMath\Helper::replace_vars( $desc, $post );
return empty( $desc ) ? $generated : $desc;
});

Hope this helps. Let us know if you need any other assistance.