Turns out I have WDS. Imagine that.
Here is the block diagram of BSD which has IBS in it (labeled Battery Sensor).
From the looks of it, there is no difference in charging from the terminals or the battery directly. However this is a functional block diagram and not a schematic. The tap at X13769 and X6404 could be a current sensing shunt which would suggest using the terminals under the hood in order to register the charge going to the battery. There must be a reason for BMW suggesting using this so I'll continue using the terminals to charge.
2010 E63 Black sapphire metallic
“Speed has never killed anyone. Suddenly becoming stationary, that's what gets you.”