Here are the requirements for attribution:
Visually indicate that the content is from Stack Overflow, Meta Stack Overflow, Server Fault, or Super User in some way. It doesn’t have to be obnoxious; a discreet text blurb is fine.
That's fine. They say: "Content from Superuser of Stack Exchange. Original article at Superuser." at the bottom.
Hyperlink directly to the original question on the source site
They do that as well.
Show the author names for every question and answer
That's in there too, also for the comments.
Hyperlink each author name directly back to their user profile page on the source site
They also took care about that.
Therefore, I don't see a particular problem with that site, at least in terms of missing attribution.
