All modern “Power Breakers” with Electronic Trip Units (ETUs) such as the WL operate by a solenoid trip coil. It’s called a shunt trip in Breakers that have ANOTHER trip unit, because the solenoid coil is “shunting” around that trip mechanism. In breakers that have an ETU, that solenoid coil is the normal trip system, so the word “shunt” technically doesn’t apply, that’s why it’s not mentioned in the manual.
But it’s just like a shunt trip, you can externally energize that coil instead of waiting for the ETU to act on it. In the case of Siemens, the ETU has terminals for you to connect your external signal wires. So for example if they want the ST functionality as part of an E-Stop or EPO (Emergency Power Off) system, you would just wire your E-stop PB terminals to that external signal input in the ETU.
Now, IF the only reason they are asking for a “shunt trip” is because they want GFPE protection and they think it uses an external GFCT that needs to be wired to an ST, that’s incorrect. It is not necessary in the WL, you just buy the ETU that provides GF trip (for example an LSIG trip unit)