It actually makes things worse really "no hackers can break this!" sounds good on paper, but it could just mean your adversary has more to gain by the system not being publicly broken.
I don't see how it makes things worse. Surely it shows more if you gave hackers a big incentive to crack your encryption and they still didn't, compared to them not cracking it when there was no incentive. It is evidence that the reason they did not crack it was the difficulty of the problem, not just indifference.
A 73 day deadline on no notice to crack the system in a very specific way with no pay for people who succeed after the first is not a very big incentive. How many highly compensated security experts do you expect to stop doing their jobs for the opportunity to work for free?
