You’re assuming that assets from before when the disclosure requirement was added are AI-free. That’s not a safe assumption. Obviously the disclosure requirement was added as a reaction to AI assets that were already there. I’m assuming the opposite: that the makers of AI-free assets jumped at the chance to mark their assets as AI-free, and the makers of AI slop jumped at the opportunity to not mark their assets as AI-generated in order to fool people who assume that no disclosure means no AI.
In the end, it doesn’t matter if the unmarked assets are 1% or 99% AI slop. Either way, they are not safe to use if you want to avoid AI slop in your game, so Itch correctly filters them out if I ask it to filter out AI slop.