It was beamed aboard the ship Leia was attached to, so its kind of minutiae, as for the Rebel spies, in the opening crawl its stated that said spies stole plans to the Death Star during a battle, and indeed, in Rogue One they stole that information by infiltrating a secret Imperial base, that's spy work yeah.
The main heist Vader is aware of is the plans being beamed from the surface of the planet to the Rebels, who intercepted it, the fact that these plans were they put onto a datafile and handed over to a smaller vessel within that ship is a minute detail that Vader may either not be aware of, or simply not prioritise. He's looking for the plans that the Rebels intercepted over Scarif, hence why he asks the question.
And from Vader's perspective they are spies, he doesn't know there personal background.
Originally posted by Total Warrior
Also, another dialogue that sounds wrong now is when in ANH Mothma says " Many Bothan died to deliver us these plans", or something similar ( don't know the exact sentence in the english dub), however in this movie we don't get to see a single Bothan 😄
Tbh I don't get how people get confused with that. We know there's a 2nd DS being built, and Mothma says Bothans got a hold of that information, the first DS is irrelevant as it was destroyed in ANH..and Mothma's line was in ROTJ....she wasn't in ANH.
How people get confused here is beyond me. The only way people get confused, is if they really, really, REALLY paid 0 attention whatsoever. Which I find extremely hard to believe, you'd have to not even seen the movies then..