I also wasn't understanding the value looking at the first two examples, but the pricing packages example I do think I would struggle to implement in a clean way using traditional css.

I'd use <table>. It literally is a table. And for mobile just do a media query to turn it into a flexbox.

Yeah the claim that tables are hard to style for such a simple design doesn't really hold up in my opinion.

This took two seconds to make https://codesandbox.io/p/sandbox/5ry4rl

I do agree though that subgrid makes the HTML more readable though so I'm all for it.