It's kind of in keeping with the new combination of Resume and auto-termination for apps, i.e - your apps are never truly "closed" since they can return with everything exactly as it was before.
Unfortunately in practise this isn't completely true as many apps will still take a while, if not longer, to re-open with Resume. In theory it's great, but relies on well-written apps that can launch quickly, which not even all of Apple's apps qualify as; I'm looking at iWork on this one, while they're all great apps they're incredibly slow at re-opening documents, and not super quick to launch either, even on an SSD.