I really can't come up with a physical explanation for differences between X100S and X100T B&W image rendering.
In fact, except for the original X100, the differences between raw renderings for XTrans and XTrans 2 cameras is subtle. In LR CC default rendering The Xtrans raw has more detail in dark regions and highlights regions have less. XTrans II default rendering is the opposite. Changing rendering parameters all but eliminates this difference. There may be more Fujifilm Film Simulations in LR 6 CC's Camera Calibration Profiles.
I don't use in-camera JPEGs, so perhaps these are different.
The main difference between the 100S and 100T (besides the prices) is the X100T Digital Split Image manual focus system. This focus option simulates a RF patch. The only other Fujifilm camera with this feature is the X-Pro 2. The X100T's PDAF focus is a nice improvement as well. This may be available with new X100S firmware, I really don't know.
“To see what is in front of one’s nose needs a constant struggle.” George Orwell