Almost all of that (excluding voicemail) is pure text data, isn’t it? There’s no way it should be taking up multiple hundreds of megabytes. I can’t imagine voicemail audio is particularly high quality, but if you do have a load of messages then I can see it adding up.
My Phone app user data is 277MB.
Google Keep (lots of notes with offline mode) is 10.62MB.
Google Maps’ offline maps for my entire local area is only 109MB.
Google made this available so they can encourage developers to use it and say “we’re not a monopoly, the developers are adding the check” and see how long they can get away with it.