That’s an interesting angle — and you're right to notice something unique.
One of the more interesting technical features of the OS X Mavericks (10.9.x) DMG (compared to previous and later versions) is related to how Apple packaged and delivered it.
While Apple no longer lists Mavericks prominently on the Mac App Store, there are still ways to secure an official installer: mavericks os x 10.9.x dmg
Groups low-level background tasks together so the CPU can stay in a low-power "idle" state for longer periods, reducing wake-ups by up to 72%. SMB2 by Default: That’s an interesting angle — and you're right
A DMG (Apple Disk Image) file is the equivalent of an ISO file for Windows. It is a virtual hard drive container. When you download Mavericks OS X 10.9.x DMG, you are downloading a compressed image of the installer. Apple shipped the full installer inside the Install