All the school sees is a regular cancellation notification, they will not see that you score previewed and then cancelled That aside, they don't care about cancels because they don't know why it happened. You could have been sick, or maybe there was a technical problem with your test. They don't automatically presume it's because you did poorly! To them it's a void they basically ignore, and instead they focus on what they can see (your score, grades, essays, etc).
Fair enough, I guess anyone with an identifying email is a better way to describe it. And just to be clear, I never said the no delete rule was hidden. It is made very obvious. Just making a suggestion to possibly boost retention