I think it was indeed that very sin. I believe you are correct.
If I rephrase your reply as, “Man chose to disobey God”, have I distorted your meaning do you think?
I hope not, that was not my intent. My purpose is to signal that I am discussing “Man as God’s creation” rather than the linguistics of the “Adam and Eve” story as allegory.
Either way, I propose the original sin was a choice Man made. Would you agree?