An EVF/live view generally does not simulate shutter speed as motion blur or freezing action. Instead, it simulates overall exposure: the camera adjusts the sensor readout and display processing so the preview looks brighter or darker based on the combined effect of aperture, shutter speed, and ISO.

So when you change shutter speed, the preview usually updates brightness, not the actual look of motion at that shutter speed. If it truly previewed shutter behavior, moving subjects would blur or freeze exactly as they will in the final image. In normal live view, that usually doesn’t happen.

In short: the camera is emulating the amount of light the final exposure would record, not reproducing the exact timing of the mechanical shutter for every preview frame.