Sorry, your comments are based on an incomplete understanding of how airfares are priced and sold. Pretty much all the major carriers - including UA - add fuel surcharges to their international fares. (Indeed, UA will sometimes offer zero fare international tickets, so they can vary the price to the consumer by adjusting the YQ, without the need to refile the fare.)

The issue is whether a particular FFP elects to pass those surcharges on to the customer. KF has elected to pass them on, the only exceptions being its own flights. Other carriers - notably including UA - have elected not to pass them on.

If you redeem for a partner operated flight through KF, you will pay the operating carrier's fuel surcharges. That is exclusively based on KF's determination to pass those charges along. If you blame TK, you are completely missing the point. Redeem UA miles for that TK ticket, and you will pay no fuel surcharges.