At a high level, the Uber assumption states that it is not possible to compute (distinguish) linearly independent elements. In the decisional version, the problem is restricted to $G_T$, but it is unclear whether the linearly independent elements can be from $G_1$.
Here is a simple example:
Let be type-3 pairing $E$: $(e, G_1, G_2, G_T, g, h)$ where $g$ and $h$ are generators over $G_1$ and $G_2$.
Given $(g^a, g^b, g^c, g^{ab}, h^a, h^b, E)$, the adversary can distinguish $g^{abc}$ or $g^z$?