alt Hacker Newsno, it sends a large “click” across the whole surface which your finger registers as a local click, they have two large and two small haptic motors in a line iirc and they do some software magic to cancel out the click so it feels extremely localised.
I just tried on my macbook trackpad and if I rest a finger in on part and click with a finger in another part both fingers feel the click. But I suspect this is a feature, not a bug, for multi-touch interfaces.