Replacing all 4 is true, zwave smart switches dont work with traditional on/off switches, as the wiring and the method by which the circuit is opened or closed are both different. I’m confused about his comment about having troubles with them, I have not heard or experienced any issues as long as the wiring is done right. Was that Home Depot tech support or GE tech support?
Usually a 3 way circuit will have the line coming into one switch box and the load leaving another. The travelers are used to connect the switches together, since either switch can close or open the circuit.
The zwave switches work a little differently. The master switch needs to be connected to both the line and the load, as it’s the only switch that actually opens and closes the circuit. The other auxiliary switches essentially just act as signaling devices, using a traveler wire to signal the master switch to turn on or off.
If you have the line in one box and the load in another with two travelers between each of the switches (and neutrals in each box), you can use one of the two travelers to extend either the line or load from one box to the other (depending on where you want your master switch), and the other traveler to act as the signal wire.