Because if it uses the same browser binary as your other web apps (tabs or other DeskGap apps), the OS can share memory between them. Not possible with electron since every app bundles its own Chromium binary.
This is just reusing a DLL and saving disk space thanks to it.
And then there's disk memory, which isn't as important IMO but still it will of course be smaller since you don't ship the whole browser stack for each application.
https://docs.microsoft.com/en-us/windows/desktop/dlls/advant...
If not, why are you appealing to iOS to help make your case?