CLS values from Page Speed Insights

Question

At the top of each report is an area titled "Core Web Vitals Assessment" and in this area is a "Cumulative Layout Shift (CLS) number. Lets call this "first CLS value".

Then within the area titled "Diagnose performance issues" there is another CLS value reported. Lets call this "second CLS value".

The first CLS value for one of my pages indicated a CLS of 0.18, however, the second CLS value reported was 0.001.

I was concerned about the first CLS value reported, and I performed an extensive amount of debugging and researching to try and determine why the first CLS value was so much higher.

Finally after running a very small "Hello World" HTML page through PageSpeed Insights (one that had no media, fewer than 20 lines of HTML with no externals) and seeing that it too had a first CLS value of 0.18 and a second CLS value of 0 - I realized that I was either missing something or that PageSpeed Insights has a serious problem.

Why does the first CLS value consistently say 0.18 regardless of what is tested?

Has something changed in PageSpeed Insights?

I tested various types of pages from my website, pages that contained a lot of media, pages that contained a single image and pages that contained zero images. I finally tested with a very small "Hello World" HTML file.