Its easy to spot AI generated arts and so far there's no participant submit a the same like art on the contest so maybe other participants are aware that they have less chances to win if they use this because for sure many people will criticize them for submitting a AI generated art. So far we can see a good submission so maybe we will mot see this kind of art at the moment.
"For now". Let's all remember that what we call "AI" right now is not something that can think all by itself, it's something that we put in machine learning and that's how it operates. If you put 100 paintings from the world famous painters then it would definitely create something good, but if I draw 100 horrible things that would be like stickman at best, then it would create terrible things.
This is why it's quite understandable that we can understand what is AI and what is not right now but when the time comes and they learn from billions of different arts and all mash it together all depending on the level of talent and understand art deeply, then we would be able to give a command to do something that would be just like a real person drew it.
It will make all these competitions mute point because it would give people a chance to participate and we would have 10-20 real people whereas 500+ people joining with AI results since it would be just a click and maybe a render time.