Why doesn't the source-shake scrip work in Studio mode? (It shakes only the Preview)

[John Hartman]

The source-shake.lua sample is a classic way to learn scripting OBS. But if you run it in Studio Mode, no shaking is seen in the Program scene.
If you have the same scene selected in preview, THAT ONE shakes.

Can someone tell me why this doesn't work (and ideally how to MAKE it work in Studio Mode)