As noted from AndroidPolice it seems that the next mobile OS version will have a notification drop-down that appears a touch different from the new layout. The leaked side-by-side screenshots show that the new layout makes better use of the available space, and will fit more notifications within the drop-down stack. the tiny extension has also been repositioned, moving upwards from the lower right corner and looking a bit more elegant.
Some of the other new features coming to Android 12 mentioned include scrolling screenshots that allow users to capture an entire page, improved split-screen multitasking, a new Google Assistant trigger, and more.
New notification layout is not guaranteed to arrive to the final version by any means and is subject to change at any time. The final Beta version of Android 12 won’t be released until August this year, so developers have plenty of time to make additional tweaks and improvements.