Mixed instrument competitions are very tricky and probably impossible to judge fairly, especially if the panel includes judges who play an instrument represented in the competition. Besides possible partiality, they know the repertoire better, as well as specific concerns with that instrument. Harp is probably at a disadvantage in such competitions, because some of the mechanics, such as pedaling and placing, can mean that harp doesn’t allow the acrobatic runs to the degree that other instruments do, and what is difficult on a harp might not sound difficult to a listener who doesn’t know the instrument well. On the other hand, some fairly simple harp effects can really wow a non-harpist, which is why we all love playing Chanson Dans la Nuit for non-harpists.
Anybody wishing to lose all faith might check out the following story, on a study where people guessed the winners of a competition more accurately by viewing silent videos of the contestants than by actually hearing them.