I believe the buyer here does not understand the leaving of feedback , and left that remark in all innocence.
They probably received a generic bot message everyone receives to ' Leave Feedback' and thought they had to, so just wrote what happened.... Cancel.
I would send the buyer a polite message explaining this does not explain the situation for others when reading it, and could affect a future buyer from buying from you.
Once understood, ask them to complete a feedback revision you can send to them.
If the above fails and the buyer does not wish to do this, just leave a polite follow up to explain the Cancellation was done promptly at the buyer's request.