Before making a case for accessory to genocide, they'd first need a binding judgement that it is a genocide, presumably. I agree it probably isn't as clear cut, or at least not as simple.
The problem is a decision it is plausible it is one isn't a ruling that it is one. There is no legal basis for deciding someone is an accessory just because it is plausible. Personally I consider it a genocide, and wish there was a legal basis for going after people as accessories, but there just isn't yet.
