I haven't experienced this but I see you're the second comment pointing that out. I've been using macbooks for work for a long time and never once used iCloud nor do I remember seeing a confusing prompt. But I also rarely upgrade my machine.
With Windows, a regular seemingly normal update appeared almost as if I was upgrading from Windows 10 to Windows 11 and it prompted me to do the backup to OneDrive. I accepted it because I was worried the update to Windows 11 would get screwed up. After the update completed it was just a normal update after all and there was no need for me to accept that onedrive backup!
iCloud nags appear in the Settings app and Notifications menu. When you are signed out, Apple will assault you with notifications (that you must disabled with a script) until you log in: https://discussions.apple.com/thread/250786208?sortBy=rank
I've got my fair share of horror-stories with both OSes, I switched between dailying Mojave and Windows 10 for a big portion of my life. Nothing will ever top updating to Catalina, booting up Ableton Live and seeing all my paid plugins go from "working fine" to "completely unsupported" in the span of an update.
I see. I think part of the reason why I don't see this (or don't remember it?) is I treat my work computer differently than my home computer. For my work computer, I honestly only restart my Mac maybe once every few months and never install updates. By the time I'm 1-2 OS releases out (usually when the battery starts to fail), my company gives me the latest macbook.
For the people in the office who use Windows they start dropping off randomly during the day as their computer decides to start installing updates during critical times.
With Windows, a regular seemingly normal update appeared almost as if I was upgrading from Windows 10 to Windows 11 and it prompted me to do the backup to OneDrive. I accepted it because I was worried the update to Windows 11 would get screwed up. After the update completed it was just a normal update after all and there was no need for me to accept that onedrive backup!