You cannot mention a macOS Beta without mentioning its twin: . If macOS Sierra Beta 5 was the engine, the Xcode Beta DMG was the dashboard.
A .dmg (Disk Image) file format is Apple’s proprietary digital distribution method. An contains the isolated application environment, complete with: Macos Sierra 10 12 6 Beta 5 Dmg Xcode Beta Dmg
Yes, Apple still provides the installer for macOS Sierra 10.12.6. You can find it on Apple's official support website or through the "Purchased" tab in the Mac App Store if you had previously downloaded it. However, Apple no longer digitally signs older versions like 10.12, making clean installations more complex. You cannot mention a macOS Beta without mentioning its twin:
: Security improvements, bug fixes, and minor stability enhancements rather than new user-facing features. : Addressed issues preventing certain SMB connections in Finder, fixed Xsan client : Security improvements, bug fixes, and minor stability
In summary, the 10.12.6 Beta 5 cycle was less about novelty and more about reliability