It's an image. None of the charts are responsive charts in HTML and CSS.

I didn't even notice the CodePen at first because it doesn't load automatically (instead displays a cropped and zoomed image).

You are correct they are images besides the CodePen, I did not inspect them before commenting (hope the images is at least the output of the code). Guessing it must have something to do with the companies hosting platform tools and authoring code to it but have no idea why.