It’s not a like-for-like comparison.
The big difference between those pages is that the TRS page is /latest while ubuntu uses /categories. Latest scrolls infinitely, categories is limited to 20 posts. There will always be a bit of jerkiness when your browser polls the server for more posts.
If you need something from the source you can look directly at the pages, but I’m pretty confident that rather than having some super-secret smooth scrolling code in their pages the reason is the above.
Please don’t tag people directly, particularly when a small amount of research on your part can answer these questions.