From a format perspective, it really isn't any different than other tournaments anymore. It's more the name and the history (and the official Major status) that give it the added prestige. Some are upset because Worlds used to (as in, before this year) feature more rounds overall and this is a break from tradition. But part of that old format had to do with involving multiple divisions and therefore more players, so shorter and less challenging courses were included for the purposes of expediency (and also because they were what was available).
Now, with Worlds only including MPO/FPO, the tournament can be run on courses that are tailored specifically to challenge the very best in the game. And with that added challenge in the design of the course, fewer holes are needed to separate the wheat from the chaff. A marathon is no longer needed to allow for the cream to rise to the top.
It should be noted that there's nothing of significance, format-wise, differentiating ball golf majors from typical PGA Tour events like the Memorial two weeks ago, this past weekend's St Jude's Classic or the Travelers Championship in two weeks. But this week is the US Open and it's special, due in large part to the history of the event.
