anwarmahmoodHi.
Bromium is far more advanced than Windows Sandbox. It does not try to provide you a sandbox for test; it puts every single app into its own isolated partition. Another solution similar to Bromium is Turbo.net, whose base tier (command-line app and virtualization engine) is free, but its services are all commercial. Turbo.net for Windows is very similar to what Docker is on Linux.
Windows Sandbox is more like Comodo Containment (a component of Comodo Firewall/Antivirus/Internet Security), Acronis Try & Decide (a component of Acronis True Image), Sandboxie, or DeepFreeze. However, they all employ storage virtualization. Windows Sandbox is, for some reason, trying to employ full hardware virtualization. (The result hasn't exactly been heart-warming so far. See above. Lots of people are complaining.)
So, no, Windows Sandbox is not trying to extend Application Guard to all apps. Bromium does it. Docker does a similar thing too. But not Turbo.net.