I recently had the fun of driving Highway 4 on Vancouver Island. There are some steep twisty sections with some very uneven and patchy pavement.
The uneven pavement on these twisty downhills had a very observable effect on regen when watching the "regen bar". It would jump all over the place, likely in reaction to available traction as the road surface rapidly changed. I found this incredibly interesting as I had it in mind to turn regen to "Low" for winter as recommended by Tesla, but they definitely seem to be accounting for available traction with "Standard" regen. Of course, by the time the car is compensating for available traction, it's because it's already noticing some lack of traction and may have put you into a bad situation in Winter, so there's that.
So that's just about regen which I really wanted to talk about given my recent trip. But in regards to ABS, slippery surfaces (or rather, applying more braking force than available traction can give) is exactly what ABS was designed for in all vehicles. It is effective in those conditions for maintaining control of your vehicle, as it is for any modern vehicle with ABS.
Notably, this is something Tesla initially messed up with the Model 3 and fixed with a software update.
Suggestion: next time it snows, find a large empty parking lot and play with it in normal & low and see what it does. I gained a lot of confidence in it last winter (LR RWD) and I just leave it on normal now. The traction control is pretty amazing on these things.