In the screenshot, I have provided you can see that it says, "The width and height attributes are used to infer the correct aspect ratio of the image and avoid layout shift from the image loading in. The width and height do not determine the rendered size of the image file."
But I have checked that it doesn't work like aspect ratio. w = {20} isn't same as w = {40}. So it does affect the render size not just the aspect Ratio.

Or I am missing something?