I’ve driven five winters, so far, with the current hardware on my May 2018 build TM3.
The rear camera does get effected, but it is not a critical path item when (even simple) TACC is used.
When the forward radar was still being employed, any coating of any freezing precipitation cancelled all cruise control operations in this car.
Salt spray on (for example) HWY 7 between Peterborough ON and Ottawa ON will coat the front end of the car in a matter of minutes.
And it does so in such a manner that if the auto wipers don’t keep up with it and then they do a sweep, the resulting streaking cancels all TACC (ADAS) systems until it is rectified (with many uses of the washer fluid button).
Your “you clean it” and “every other car” answer doesn’t change the issue: the ADAS systems in these cars don’t work when covered in salt spray.
If every other car on the road in eastern Ontario between mid December and mid March suffers a loss of simple cruise control operability because of salt spray on a front bumper camera, I would have expected to hear something about it by now.