A roundabout (traffic circle) was installed last fall not too far from my place, at a busy intersection. The change hasn't made it to any of the maps I've used (including Google, Garmin and Apple).
Last Tuesday, 11th March, I submitted this error/change to both Google Maps (via Google Maps app in iOS) and Apple Maps (via both the iOS app and TomTom's Map Share Reporter site).
Google emailed me straight away that they're reviewing my submission. In contrast, no correspondence received from Apple or TomTom - I have no idea if anyone reviewed it, let alone received it.
Today, March 17th, Google emailed me and said that they've verified my report and have made the changes. I went into the Google Maps app on iOS and sure enough the traffic circle is now there.
Still nothing on Apple Maps. On TomTom's Map Share Reporter site the traffic circle is also still missing but my report (red icon on the map) has a green check-mark on it and status says "Accepted", which according to TomTom's FAQ it means that at some time in the future this change may appear on maps using their data.
Of course this one instance, in and of itself doesn't explain everything but to me it sure shows the distinction between Google and Apple/TomTom in how map errors are handled.
In Google's case they were extremely prompt, they fixed it inside of a week. On top of that, throughout the process they were constantly and directly interacting with me to keep me posted of the status. Love them or hate them, it shows commitment on their part to this product. With Apple/TomTom, not so much.