I notice they have them on inputs *and* outputs. That, and the fact that the values are a bit high for termination resistors tells me it's more about noise suppression than series termination. They are probably trying to limit edge/transient currents into the IC, so as not to corrupt measurements of the input signal by developing transient voltages on the IC's internal ground reference.
Usually, when series terminating a PCB transmission line (trace), you'd add them at the source, or at the destination, but not both. Also, MOS outputs have typical output impedance of around 10-20 ohms. If you add that to the 100 ohms, then the traces would need to have a 110-120 ohm characteristic impedance for these to be proper termination values. That would be a *very* narrow trace, and/or a *very* thick dielectric layer. Typical traces are in the 50-75 ohm range, so series terminators are usually in the 30-50 ohm range (taking into account MOS output impedance).