I think it reflects the inherent biases in the design, training and implementation of the ML algorithms that drive ChatGPT: Science topics are considered "less uncertain but more complex" because its source material, creators and developers believe that, but also it has controls in place to avoid saying controversial things and topics like ghosts, history, art & religion are all much more likely to have controversy and therefore be more "uncertain" to ChatGPT when it comes to giving answers.