The extra width is in the back on your sitbones, so it does not chafe anything.
If you get the NON-S model, the transition is longer from nose to seat.
I have the B68 (non-S) and am not having chafing on 60 mile rides so far.
A lot depends on how wide you are and on how your thighs are shaped, etc. I'm a "pear" shape and neither fat nor skinny, but I have some padding on my inner thighs fer shure.![]()