Google offers three core website vitals for WordPress,
Explaining WordPress core web vitals and how it impacts user experience
For instance – Your WordPress website might load faster but, the largest content may appear a bit slower than the rest of the page. Several other speed test tools will give a good score but, the user still feels it’s slow.
For example – When you click a link on the website and couldn’t do it because the content shifts after being loaded. The user feels a terrible experience and layout shift. The same happens when you click the wrong button because of the late-loading content.
Similarly, if you go through a news website where content keeps shifting around along with ads. Users are unable to read due to layout shifts.