If you find any errors in the math, please let me know! I think the diagram supports your description — even with the wheel turned to the max, you will never hit anything close to the back wheel when reversing (both wheel axes are marked), although the geometry will depend on the car specs like wheel base, overhang lengths and car width (the viz is for my car, Hyundai i30 2018). Also, I just looked up top-down views of reverse turning on YouTube and it seems to match. [1]
The problem in my case is that the road is so narrow that it's very easy to hit the barrier on the right when reversing while turning to the left — that was what prompted me to make the visualiation.