Problem with Light Passing through Flat Glass in Blender

In Blender, I want to simulate an effect where a beam of light passes through a glass plane deformed by noise and is refracted into variously shaped light spots. Since I want to simulate a real physical effect, I start by trying with a flat glass plate with IOR = 1. I plan to gradually increase the deformation and IOR. However, I found that when a spotlight passes through a pure flat glass with IOR = 1, the light is scattered. This does not conform to my prediction based on the real physical world and is even far from it. Is it a deficiency of the renderer or is my prediction wrong?