my own experience is that in the city the bell was to alert people that I think aren't paying attention to me and may be about to step into the bike lane. 100% like you said, I'm letting someone know I'm there
Now that I moved to the country with a comprehensive rails-to-trail network, I thank all the cyclists that use the bell to let me know they're coming up behind me. What really irks me is the dudes going 30+mph silently coming up behind me, passing less than 2' from my dog (who is at my side) when there's PLENTY of room to give me space. No, we can't hear them coming all the time. Yes, it's startling, rude, and dangerous for all of us.
In Germany it's illegal to drive bikes that assist beyond 28km/h (about 20mph) in what are true bike paths (which can be built as lanes! And, notably, they can be marked as virtual-lane-shared (pictogram side by side with a vertical divider) or as true shared (pictogram above and below at a horizontal divider), if pedestrians are also allowed to use them.
An ancient gas-e-bike rating is allowed on them outside city limits but iirc those bikes are exceedingly rare since even before e-bikes became truly mainstream.