Currently, importing future system times will result in undefined behaviour (e.g. #4724 (comment)) and is not supported, however users are still able to do it and cannot easily recover from it (less of a problem in a dev context, but in prod could be disastrous).

Instead, transactions with imported future systems time should fail if the timestamp is greater than the log append time.

Note that such logic may also need to account for the current 'smoothing' logic that exists.