You're not meant to use the method I gave in conjunction with the confirmation checker.
The confirmation checker (in simple terms) works by telling Steam every X seconds: "Hey, I wanna confirm everything waiting to be confirmed". It will tell steam even if there is nothing waiting to be confirmed thus the load it puts on servers - imagine loads of bots doing this.
Whereas the method I put tells steams servers: "Hey, I wanna confirm this specific trade". Therefore, it only tells steam when there is something to be confirmed.