My theory on the subject of spies:
Breden isn’t a kryptast, they’re exactly who they appear to be, that is to say a charismatic helot…whose job it was to quietly draw in subversive elements from the helotry to be culled in the harrowing. The rebellion itself was an unexpected outcome. Frame Breden’s actions as a small-scale spy way in over their head. Breden is highly suspicious and does little to allay those suspicions, so probably not a professional. Also explains why they get picked for the harrowing as well. The Hegemony wouldn’t execute a trained spy for doing their job, but some random helot, who may very well begin to sympathize with the dissidents they work against? Disposable. Toss them out with the rest of the trash and voilà, no loose ends.