Is the solution here not simply to turn off mobile data when you don’t want to use it, if you’re on such a restrictive mobile plan?
The fact is, the behaviour changed in a way that wasn’t made clear at all. That WiFi will reconnect by itself after being off for a period is a security and privacy issue, and is a frustrating change.
Hiding things behind 3D Touch is not very intuitive or user friendly. What was once a toggle - on or off - is now a three state option where one of the stares can only be accessed from the settings app.
Or add warning and cut-off thresholds, isn't that alredy possible?