In my experience recovering from a herniated disc and subsequent surgery, position is more critical than shock absorption. Spines are mechanically complex and back issues are unique, so YMMV. I iterated with my bike fitter to find a position that minimizes low back pain. I also add on-bike stretching, which helps tremendously after climbs or long efforts.
Having said that, I do run either 32mm or 35mm tires on my brevet bike.