I consider it a mistake because it's utterly contrary and different from the rest of the games. But perhaps mistake is the wrong word... I think that whoever did it, did it intentionally, but I do think they screwed up. Remember, TP was NOT made by Miyamoto.
There are other examples in fiction of whole species being named after their native land. In the Narnia books, for example, the Telmarines (sp?) came from a land which they were named after, but they were the only humans in Narnia, at least during that time period.
Well, actually, the thing about the "tribe" term in Zelda... ALL the species are called "tribes." Including the Zoras, Gorons, and even the Rito and other species throughout the various games.
I know about racial differences on earth. But this isn't earth. First of all, if Sheikah (which are specified as a tribe) are the same species as Hylians, they aren't the same race. They have red eyes and if I'm not mistaken, white hair. Hylians don't.
And I really doubt the Gerudos can be of the same species, as they have utterly different breeding traits. Unlike Hylians, and well, every other species, Gerudos only give birth to a male every 100 years or so. For that to happen, they would have to be far more genetically different than it would be possible for them to be considered the same species, in my opinion.