Why does Wordpress list all image sizes in srcset even if they're larger?

For example we have the following sizes: thumbnail (400), medium (768), large (1200). If we use the_post_thumbnail('medium'), Wordpress generates the following image tag:

img width=768 height=768 src=https://example.com/wp-content/uploads/2021/12/my-image-768x768.jpg  class=wp-image-318 size-medium srcset=https://example.com/wp-content/uploads/2021/12/my-image-768x768.jpg 768w, https://example.com/wp-content/uploads/2021/12/my-image-400x400.jpg 400w, https://example.com/wp-content/uploads/2021/12/my-image-1200x1200.jpg 1200w sizes=(max-width: 768px) 100vw, 768px

My question is: why provide the 1200w version? sizes attribute guarantees that it will never be used. I know that srcset can provide Retina-versions of images, but as far as I know, they should be explicitly listed as image.jpg 2x. I don't think that browser will see 1200px version and will automatically try to use it because it's as close as it can get to 2x. Or am I wrong?