Something i especially appreciate about winget us that it will "index" (or whatever you want to call it) software that was installed outside of it. For example if I install app XYZ through an .msi setup file, I can update it using winget.
So it seems I can also use scoop or chocolatey to install new software and then keep managing them through winget.
Depends on the devs but I reckon they won't use the API.