This is a problem with all kinds of apps. There is no discipline in the handling of user data. Take the notes app. When you delete text it not gone you can still see it in the sqlite database they use for storage. I'm sure this is so they can support sync be recording your changes as CRDTs or something.

And if the app isn't leaky, the OS will probsbly screw you like in this case. The concept of being able to clean up your laptop is just not supported, you have to wipe the whole device which is ridiculous.