Why is limited regen in cold weather a thing?

[Daniel in SD]

Think about that a little more.
First you would have to get the regen energy captured before it gets to the battery, so there would have to be some sort of high voltage switch placed in the cable between motor and battery with some kind of sophisticated controller that limits heater input to a safe amount of power.
Then there would need to be a heater that can take high voltage, or an additional DC/DC voltage reducer installed in front of the heater.
There would have to be an additional loop in the battery cooling/warming pipes.
That heater would have to somehow operate with non-continuous power supplied at odd intervals.
And where would they find the space for these additional components?

Maybe not "so simple to convert electricity into heat" after all.

That $580 heater I posted has all that in it and it's not that big. Just have the coolant loop go through it. It would just be wired in parallel to the battery.
I wonder if they could program the motor controller to be less efficient and generate more heat in the motor.