The option is there for role-playing purposes. It does have consequences for Chapter 12 and it is mentioned again when you return to Ishari but no one is going to hold it against the MC because the Nomad Tribes and Ishari have been clashing against each other for years. If you follow Anu's path, you're there to gather information on their weaknesses, not to build an alliance. Wars can be won in more than one way – at this point, people don't have time to sit around and mope about failures/lost chances because of the battle that's coming. I hope that clears it up for you! Please note this is also a first draft. Some scenes are bare-bones right now and will be fleshed out during edits.