Key words there are ‘sin no more’.
The Jews knew what sin was. They had the word Of God that told them.
Jesus did not say the woman didn’t sin. He was saying she did and should stop doing what she was doing that was a sin.
He simply stopped the stoning.
The LAW said a thing must be settled by 2-3 witnesses.
None came forward.
The stoning had to stop.
“Neither do I condemn you.” Jesus was not WITNESS to the event that precipitated the stoning.