Sure, infected in 2372, but what was the lead time on developing the virus? Surely it didn't spring into being the minute it was wanted. Clearly someone in the Section 31 leadership, if such a thing exists, saw a potential threat years ahead of anyone else in the UFP, and had a weapon prepared in the meantime. Sure enough, the situation degenerated, and the weapon was deployed.
Making a biological weapons to wipe out a race when it still hasn't been determined if a major war is avoidable or not or even how destructive said conflict would be doesn't make Section 31 sound better.
It's not supposed to make them sound better. It's an observation that makes them sound worse. They are