All the freeze-tolerant ball valve is designed to do is protect the valve itself from cracking by the sacrificial disk (freeze plug). 90% of valves crack over the winter when the water is off for the year, then in Spring when the water is turned on any damage will appear. So it will be easier to screw out a plug than retrofitting a new ball valve.
This device is for protecting the ball valve, not any piping.
If the system is on, and the ball valve is in full open position, and a hard freeze occurs and ruptures the plug, the plug itself is isolated from any pressure in the system because a ball valve isolates the sides... that's why the sides crack- water is trapped inside without any escape. so there is no threat to flooding in that scenario.
At the end of the day, any damage done by ice is not a warranty issue, but rather a maintenance issue. All manufacturers of pipes or fittings or components such as backflow devices make the same claim... basically that a person needs to protect their system by proper maintenance procedures ... insulating/ draining/winterizing etc.