[quote="Azdgari"]Also, given that that is an unofficial website, I don't put much stock in what it has to say, at least not when it makes no sense to me.[/quote]
In hindsight, that probably wasn't the best site I could have linked to. Brian Tiemann, the maintainer of that site, actually attended the TLK 10th Anniversary Panel, and he was the one who asked the question about Nala's father. He's included a full write-up of the event
here, and there's a write-up from another attendee that features the same info
here.
In the directors' defense, though, they obviously hadn't given the topic much thought, and in their own words, they "hoped no one would notice" that there were no males in the film that could have fathered Nala without making her related to Simba. They probably threw Scar and Mufasa's names out because they were the only candidates that they knew of. If only they had heard of TLK6NA... : )
But we fans tend to have a history of disregarding official information. When the news came out that Nuka and Vitani weren't Scar's cubs, many of us refused to accept that information (especially in Nuka's case); some of us think the official story of Taka getting his Scar from a Cape buffalo is lame and make up our own explanation; and I'd guess that a good 90% of fans say that neither Mufasa and Scar fathered Nala. (If Scar is her father, he seemed pretty nonchalant about having her killed by the hyenas ["I practically gift-wrapped those cubs for you..."], and then there's the scene where he's hitting on Nala in the musical...)