Hi, thanks for asking! It's not a stupid question. I'd like to find better wording for the rule in the future.
Research and development is very broad, everything from deciding what type of game/project you're making and how you're going to make it to the process of actually making it. It would cover things like asking an LLM for ideas or inspiration, using an LLM for writing / debugging code or writing a script, making art that is based on an AI image even if the AI image itself isn't used, or anything else that uses AI in the process of making or planning the game. It refers to generative AI, nothing to do with AI in the sense of enemy behaviour in games etc.
The reason for the rule is because of the environmental impact of AI, as well as it stealing from artists etc.
It's an intentionally strict rule because every week there are multiple AI submissions and I don't want to waste brainpower on whether someone broke the rules or not if it's clear they used AI. It's not fully enforceable in that there's often no way of knowing if AI was used in the process, so it does ask people to be honest about it. AI is also hard to avoid - search engines often give unwanted AI overviews etc. - the rule isn't about those cases.
Let me know if you have any other questions!