It's the combination of cold weather and low battery SOC that is the issue...if it were warmer, it wouldn't be as much of an issue. Note, if the battery is cold soaked, it also may take awhile for the management system to warm it a bit before it will reach maximum charging rate.
FWIW, I've 'lost' 10-miles of range just from the temperature drop considerably (from my garage to outside) overnight. It could be enough to mess with the 12vdc battery, too, which doesn't like cold. The system won't recharge it unless plugged in, and that's necessary to run the computers.
2011 535i x-drive GT, 2014 i3 BEV