Hey BelYT - that is a requirement, yes. To enter, everyone has to upload additional work-in-progress images in the 'show development work' section that you'll see under all of the entries. and also on the submission page for this reward. We won't go through the submissions or those development work images to this reward until we judge it, but once we do, if we discover development images that we deem to be insufficient proof of originality, then we'll reject the entries.
Long story short, if there's any chance your entry could be mistaken for AI, please include the best proof of originality that you can.