This chapter is what leads me to believe that prior to this point, Achamian (and the rest of the Mandate) are practically unwitting agents of the Consult themselves, at this stage. Much of the chapter is world- and character-building, but a couple of things stand out to me.
Simas being replaced by a skin-spy was likely not a recent thing, I think at least pre-dating Akka's apprenticeship in his youth. Simas was his tutor, and especially the stuff like Simas' "There's strength in scepticism ... enough to be sceptical of our scepticism, hmm?" It's the beginning of the argument Simas makes that finally persuades Akka to betray Inrau, because it had trained Akka to think that way. It realizes that doubt is at the core of Akka's worldview, because it trained him to be that way! And likely many others among the "sceptic" faction.
It then continues to invoke the Mandate mission, to press just how Important Stuff this mission they're giving him is. And it is, to the Consult. We learn that Maithanet has an unusual affinity for rooting out spies and plots. With the relatively recent discovery of the skin-spies a decade earlier, I think they're hedging their bets. They still don't know why their spies were detected, and though they do have agents within the Temples, none seem to be close to Maithanet. Sending one of "their" human resources could seem a much safer bet.
And in the end, it's subtle enough that Akka feels like he is agreeing with Nautzera, though it is Simas who persuaded him.