Well, it would be extremely hard to catch is the problem. Someone is using off-site for the contest with no itch version available to download (unless they have one that is only for judges). I'm not saying that they have, but if they were to choose to change their files and they knew how to mess with timestamps, it would be potentially possible for them to update without anyone realizing short of someone seeing that there was a difference in filesizes or gameplay after downloading later on.
IIRC, this happened in another jam where the files did change.