OK People - Relax....deep breath...
Ben - The Surface Pro 3 is unlike any of the other devices you mention above as this device is a Connected Standby enabled machine like an ATOM or ARM Device with the exception that the Surface Team modified the S0iX Spec to enable a Hybrid Hibernation Power Scheme to allow for longer battery life while not in use....
This design decision is what causing the Alarm not to work for periods of inactivity lasting over 4 hours.
I use my Lumia 1520 for my Alarm as it does what I need.
That was the best explanation yet. Also I'm so jealous of all of you 1520 owners with SP3's though.