I have come to a personal conclusion that john gained his retcon powers from interacting with the house juju and has nothing to do with his classpect.
I mean, no, John definitely gained his Retcon Powers through touching the House Juju and that’s very explicit. However, I’m just saying that ‘detachment from the story’ and ‘freedom from the alpha timeline’, and ‘inflicting change on the plot’ are very Heir of Breath-coded things. The question isn’t whether he got his Retcon Powers from the House Juju, it’s if the House Juju gave him new powers, or if it just supercharged his Heir of Breath powers, much like how the Sucker supercharged Jane with Life.