Don’t believe that. With a slow plane with a 18000 feet(ish) ceiling, you can and will circle all day on the mountainside with upwinds, until you have enough margin to make it over the pass. On that CAVOC day you can make that judgement only with visual clues. That they run out of performance only if they had engine troubles. And even then you let not get it into a corner but start a fly or glide to some decent emergency landing area early. With two experiences pilots that should be no task overload. One flies the airplane and the other deals with the technical problem. With such a relative low tech bird with mechanical control surfaces should be not much problem. I am sure there is more to the story and that will come out.