Conspiracy theory time! Apple puts this out there to break iPad-based DIY home control panels because they're about to release a product that would compete with them.
> Apple puts this out there to break iPad-based DIY home control panels
If you were using an iPad as a home control panel, you'd probably disable the passcode on it entirely - and I believe that'd disable the inactivity reboot as well.
I can't imagine how "time since last unlock" would even work for a device with no passcode, since the user never explicitly unlocks the device. Besides, a reboot wouldn't do anything useful in that configuration; with no passcode, user data is always accessible.
If you were using an iPad as a home control panel, you'd probably disable the passcode on it entirely - and I believe that'd disable the inactivity reboot as well.