This rule is a motivation keep your equipment under control. It was adopted as a way to prevent a shooter simply shooting an arrow into the ground instead of letting down safely.
If you cannot let your bow down under control, you are not within your safety envelope, whatever that is.
Soo-o-o, I would suggest as a basic guideline that if the string propels it, it is shot.Fingers or release still on the string is a good supporting argument.
A shooter cannot waive safe conduct in any circumstance. Whether a shooter can recover a shot arrow within his reach may not apply.

With all that said, I do not believe that we cannot wholly clarify this one to cover the eventualities. Each of us has a reasonable level of common sense that can and should dictate if it is, or if it ain't.
If during competition a shooter looks to call it a shot arrow when common sense says that it was dropped, would also fall into aother category.

ken12