The "columns" are 3 sections, the last two flow between being side by side or stacked, depending on your browser width. If you make your browser narrower, the "middle" and "right" stack to become very close to the length of the "left" block.
You are just being penalized for expanding the width of your browser past the design intent. 🙂
Seriously though, free placement of all items would be nice, the sticky part is how you handle displaying it to different browser widths. If you open the site in a tall skinny browser like a mobile phone in portrait mode, do you force left right scrolling, or do you flow everything vertical? If the browser is then expanded side to side, do you create more and more columns?
(Disclaimer, I am not a web developer, or involved in any way with the layout or design of Unraid. I'm just pointing out that it's not quite as simple as it sounds on the surface to make things look good for multiple layouts simultaneously)