In the past, apps used to populate the LaunchServices registry were those located in the traditional Applications folders, but recent versions of macOS have extended that to cover almost any accessible folder. This has been explored by Jeff Johnson, who has shown that excluding folders and volumes from Spotlight indexing, by adding them to the list in Search Privacy… in Spotlight settings, will exclude those apps from LaunchServices’ list. If you make the host’s Applications folder a shared folder with the VM, then open that shared folder within the VM, all the apps within it are promptly added to the Open With… list in the guest, a behaviour likely to be unwanted.