Reading the rules I had gotten the impression it was a recommendation for our own benefit to ensure no one tried to steal your art, not an actual restriction. It states, "Please refrain from sharing your artworks publicly until the winners are announced, in order to protect your Entry."

Notably, it starts with "please" when the other bullet points state you "must."

I saw someone on Twitter sharing their design as a sample of their submission instead of directly sharing what they submitted on the provided template. That seemed like a good work-around as it keeps anyone else from having access to the actual file they submitted to try and claim it was their own later if it wins or something crazy like that.