You have to use at least some domain knowledge, else you would be making a general-purpose artificial intelligence. The rules actually say: "without relying heavily on human domain knowledge" (emphasis mine).
The rule is actually quite vague, which is not very surprising, as it seems quite hard to define what domain knowledge is allowed and what isn't without having lots of loopholes.
I agree that is vague. But there are plenty of RL algorithms that learn with essentially no domain knowledge, e.g., MuZero[1] which doesn't even use a model. That doesn't make it AGI -- it only masters a single game at a time and we currently don't know how to transfer that knowledge to other domains.
