[Reaper45]

It states the only Legion to pose a genuine military threat...

I don't know. Maybe the Wolves were destined to be on the fields of Istvaan V, but instead of being shocked by the betrayal of their brothers, the Wolves would have rallied the Salamanders, Iron Hands, and Raven Guard and blasted their way through the Traitors and made good their escape?

But this is before Istvaan III, much less Istvaan V (which wasn't originally planned by Horus...his hand was forced when the Eisenstein escaped).

Then again the Warp doesn't give a poop about linear time, so who knows?

At this point The wolves were probably the only legion to successfully wipe out another legion.

Perhaps They would have saw through the deception and realized what was going on before the trap fell?