Sure thing, I will be 100% direct:

Deadlock is third person (over the shoulder). Dota is third person (3D rendered top-down). These two forms of camera are named after the literary convention of third person narration in literature. Literary third person, like gaming third person, comes in a variety of forms, typically characterised by the level of omniscience of the narrator. You and WereCat are using third person as a shorthand for over the shoulder because you have poor critical thinking skills and prefer to mindlessly repeat the words you've heard other use. Other people typically use third person in video games to refer to shooters, contrasting it with first person. There are no isometric shooters, unless you count bullet hells. While isometric games are also third person, people typically choose the shorter name of isometric when applicable for convenience. The Wernicke's area of your brain has therefore decided that isometric games are not third person, because it works on correlations, not on logic. You neglected to use your conscious powers of logic to question your assumptions, because you're lazy.