Whenever I've tested ChatGPT I've never seen this autocomplete. Does it only conditionally appear if someone is logged into their service? I also only visit under Linux.
Given that the completion of "What is the history of Fr" is "What is the history of Fringe theatre and its impact on the arts?" and for "What is the history of G" it suggests "What is the history of Glassmaking through the ages?" I'm pretty sure this is a discovery mechanism using a fixed list of safe, quirky topics, rather than a serious attempt at predicting the user's next word.