no, it's not really a rule, but rather a recommendation.i have one question, is the "only submit 3 concepts not 4 or 5 just 3" still a rule? I reported more then once, a 4th or 5th concept and nothing happened
We still hope that when the contest holder asks you to do some modifications to your previous entry you will provide a revision and not a completely different design. Though when the contest holder is not very clear about that and still marks your design as "needs work" you are free to either update your design or submit a new concept.