Length of free trial
After purchasing my phone I got an email from Apple: "Your new device includes Apple TV free for 1 year". Once I subscribed, Free Trial states it only lasts 1 week.
iPhone 7, iOS 14
The offer is for those who purchase qualifying hardware, which would include iPhone. It then needs to be claimed within the TV app on that device once setup. If it only shows one week then one needs to contact support, however if they proceed to claim the standard 7 day trial then they would no longer be eligible.