Theses reports seem pretty anecdotal. Is there some hard evidence or an official spec? Seems like a bunch of people with glitchy phones or batteries blaming the weather.
It has only happened once, but I doubt the phone is faulty - it instantly went from a charge in the 40% range to a 'plug in now' screen, eventually returning to normal with the same amount of charge once I got out of the cold.
Could be that different phone models behave differently in low temperatures?