Assuming the Model 3 is very similar to your rear-regen S, can you actually describe how that makes sense? I'm going to disregard your statement about the AWD going bonkers, since I always am outfitted with winter tires - must have been fun though!
I understand feathering the accelerator in order to slow down while in regen in order to prevent lock up in a 'driving-straight-on-ice' situation. That's very analogous to feathering the brake in an ICE.
If you are in a turning situation on ice, and you need to apply brakes in an ICE, it's a simple feathering process as well, as the brakes apply deceleration to both the front and rear axles, and all sorts of ABS/traction control can help. However, if you are driving on an icy road in a RWD Tesla and you round a corner and need to slow down, your options are to feather the accelerator to bring about enough reverse torque to slow down, or to apply the brakes (which means full-regen and friction brakes which I presume is an aggressive slowdown). But in the middle somewhere, you have applied too much reverse torque to the rear wheels, and now they've locked up, spinning you into the ditch/oncoming traffic/getting lucky and staying in your lane somehow.
Am I missing something here? I'm not ranting for the sake of argument; it's my ~$5000USD question. This is a serious concern for me. I do a lot of back country skiing and snowboarding for about 6 months a year, so I'm on all sorts of mountain roads in any type of conditions and temperatures imaginable - being a snow chaser means that if there are warnings for people to stay off the roads, generally means I'm on them. I'm not sure if the current Model S/X demographic fits my audience in which Tesla may not have the data/experience in this regard.