I think you said your experience was with good snow tires (good on you for using them). With respect, you may not be experiencing the limits of traction very much. You're right, of course, that feathering the accelerator can prevent the rear-wheel slip...but you have to feather because the regen brake force distribution is wrong. Or, put another way, if the regen brake force was better distributed (as in is with off-road assist) you could get more regenerative braking force and control before the tires slip. To me, that's just better performance, period.
So yes, it is definitely a good idea to drive smoothly in the snow, and that will certainly minimize slips...but Tesla could make their cars perform much better in the snow (and tolerate stronger regen braking) if they had a traction mode that got the regen brake force distribution more even between front and rear. And, bonus, folks who pull their foot off the accelerator in a dicey situation (which is an ingrained and pretty sensible intuition) would not be fishtailing around.
Incidentally, I think I heard somewhere that the gearing between the motor and wheels is different front/rear, and that Tesla is trying to use the most efficient effective gear ratio by changing the blend between front and rear torque for both acceleration and braking. That's fine when traction is not an issue, but we NEED a mode that limits that rear-wheel bias for regen braking but doesn't defeat traction control (as off-road assist does).
