I did think, “What is utop? It’s a better toplevel? What’s that? What’s a toplevel? Never heard of that. A REPL??” There was nothing intuitive about calling it a top level, for me. I’ve never seen “toplevel” used in any other language. (I learned lisps a long time ago, and I have no idea how well-known “REPL” is outside of functional languages.)
It’s a small hurdle to get over, but if there are many small hurdles, they can have an impact. None of us has time to try out all of the technologies that are interesting and potentially useful. Many would turn out to be … not worth the trouble. So we make judgements as we learn about whether something is worth learning. I don’t think one should disdain attempts to make potential users take that the next little step to learn more about what began, perhaps, as only a casual curiosity.
Adding a toplevel = REPL note may be enough in this case. “Interactive prompt” gets the idea across, too.