If your intent is to make it a pure human-keyboard-code challenge, then I would have thought this would be a great opportunity to make the underlying questions harder, or to find the edge cases (in terms of input or question format) where LLMs are no help.
In the same way, a human competition in advent of code is an interesting challenge--and wouldn't be, if people cheat with AI solvers.
The point of AoC was always to practice something new, learn a couple of things, challenge yourself a bit, share solutions and ideas with people etc. I don't see how that's changed by the existence of LLMs or by this policy.
Isn't every coding competition pointless busywork? The organisers already know the solution, and even if they don't I can probably find a dozen solutions on github/reddit/wherever.
The point is you can enjoy it even though it's pointless busywork - much like you can enjoy doing a crossword, or running a marathon, or lifting a heavy weight in the gym.
Even then, it seems like something being beatable by a computer doesn't make it pointless to do as an exercise. We still teach children to add and multiply, even though computers can do these things billions of times faster than a human can and have been able to do so for decades. We believe that being able to do these things in ones own head is valuable even if it isn't the fastest way of doing them. Besides, there are still many people who practice and enjoy chess even after computers beat humans at it, and in fact many people integrate computer chess programs into their practice and analysis of chess.
The advent of code problems are already "busy work", in the sense of not making much sense, and having numerous complexities thrown into them for the sake of it. People have still enjoyed them for the competitive aspect, or for the fun of solving a puzzle. Those aspects don't change when you introduce an AI that can solve them faster.
If you can't solve the problem in a few seconds/minutes you will be able to just look up or copy/paste the answer for every AoC day from the associated solutions thread.
So in other words if you view it like that there was already a better "tool" to very easily "solve" any AoC problem: internet search.
If all you care about is getting a number to put into the website to get a checkmark that is.