[sneak]

> While this has left a long tail of inconveniences, many resolved and some not, I am very confident that using 1 app on my iPhone/iPad will not leak data to another in any case that I am likely to care about as a non-significantly interesting person (political figure, etc).

Log in to YouTube with one Google account. Log in to Google Drive with a different one.

Google knows that both accounts are owned by the same person, because Apple lets Google's apps access the data of the others on the same system.

[criddell]

I don't think it's something special that Google is doing. I suspect they are just using the built-in App Groups functionality.

Basically, it's a way for different apps from the same developer to share information via a data container.

[sneak]

Correct. Apple is leaking the data between apps for them.

[criddell]

I wouldn’t call it leaking when it’s done by design and is something any developer of multiple apps can do.

For example I wouldn’t say Linux is leaking data every time an application uses fopen.