Can't understand 3-way switch diagram for smart switch

Question

I'm replacing a traditional light switch for a smart one (S1). This switch is connected in a 3-way with another traditional switch (S2) which won't be replaced. So in the end it's one smart and one traditional switch in a conventional 3-way connection.

The wiring instructions include the following diagram:

I understand most of it except this: if S1 is powering the red/black wire how can S2 turn the light off? Is that because the electricity would go through the jumper and then through the blue/red wire back to S1, kind of a "shortest path"? If so, would that consume electricity when the light is off?

Thank you for your inputs.

PS: please pardon my terminology, I'm not familiar with the subject.

Answer 1

S2 doesn’t power the light.

The blue wire provides a signal to the smart switch (S1) telling it to switch on/off the light when S2 changes position.

This approach uses existing wiring if converting from a conventional three-way switching and minimizes the hardware in the smart switch by only requiring a single device to control the load current.