I assume the issue would also occur with a RWD ICE vehicle. But probably you have not had one of those in that driveway? Definitely this is something that might take many people by surprise, since RWD vehicles do tend to be more rare.
A bit more charitable explanation would be that people in snowy climates probably get it in their mind that their AWD vehicle (which is probably the predominant Model 3 vehicle in these climates) will behave similarly to their previous AWD or FWD vehicles in this situation. But the Tesla Model 3, when turned off, behaves like a RWD vehicle - the front wheels are free to roll when the car is off.
Excellent point.
Also, when a FWD vehicle is placed in "Park" the front wheels are locked, and that is where the majority of the weight is located in a FWD vehicle. Furthermore, with only a few exceptions, using the parking brake on a FWD vehicle will also lock the rear wheels, thus providing the best possible situation to prevent sliding on an icy, sloped, parking spot with all four wheels helping keep the car from sliding. (However, a FWD vehicle would be still be likely to slide if parked facing uphill on a steep slippery slope if just left in "Park." Because Physics.)
A Model 3 is far more evenly weight balanced, and ONLY the rear wheels are locked. Thus there is a slightly increased possibility for it to slide once you release the regular brakes. Then you go from four wheels locked to only two. This is exacerbated when parked facing downhill. (Because Physics.)
I wonder if there might be a software fix for this human error? The car could apply some limited front service brake pressure if:
1. Temps at or below freezing.
2. Vehicle parked facing downhill on a steep incline. (Because Physics.)
3. Temperature has not increased above freezing for more than 12 hours.
4. Front wheel rotation exceeds 2 or 3 degrees.
But keeping all that processing going, and front brake pressure applied for an extended period, would take battery power and possibly cause wear to the ABS Module.
Interesting interaction between Human Factors and Physics resulting in sliding Teslas however . . . .