وَاللَّهِ إِنَّ الْخَبَرَ صَحِيحٌ.
By God, the report is surely correct.
An oath and inna strengthen an assertion, but rhetorical force does not itself verify the claim. The form of emphasis and the factual truth of the statement are distinct matters.
A complete analysis identifies the declarative form, names its reinforcement, and then assesses whether the situation justifies that reinforcement.