Is Imposter Hwi rewriting his memory or is mc going down to memory lane? Or both?

i would like to think its the current hsi making him go through his past again emotions and all so he revisits The important thing and then will bring him back to the present so there can be some kind of plot point reveal or inner conflict resolution within Chang. just speculating tho. cause i think there is little to gain from "rewriting" or changing anything that was or is a part of Chang, his life, his existence.