It's a narrative device.

Clearly Oppenheimer's security clearance is an issue and the writers and the director want to show what happened with regard to the clearance and whether Groves would clear him knowing what he now knows.

In fact, much later in the movie, Groves *does* answer the question.

>Under my interpretation of the
Atomic Energy Act, which did not
exist when I hired Dr Oppenheimer
in 1942... I would not clear Dr
Oppenheimer today if I were a
member of the commission.