why doesn't this CSS snippet show up when I inspect the site and look at the style editor?

@media (prefers-reduced-motion: no-preference) {
    :has(:target) {
        scroll-behavior: smooth;
    }
}

It works on CodePen:
https://codepen.io/albinkarlsson/pen/BabRWQP

I got this CSS snippet from Kevin:
https://youtu.be/cCAtD_BAHNw?t=240

I'm also using Tailwind CSS and there is only one scroll-behavior in the hole CSS file