That is enormously disingenuous to try to equivocate IE/Spartan/Edge's single-OS existence with Safari/WebKit.
WebKit works on every major operating system, including Windows and Linux. IE/Spartan/Edge does not work outside of Windows.
There are some minor feature differences between WebKit, OS X Safari, and iOS Safari, but the reality remains that WebKit exists on Windows, can be built on Windows, and can be used on Windows, while IE/Spartan/Edge works on nothing but Windows.
Edit: I'd love to hear from the ethically bankrupt downvoters about which fact in this comment they are trying to hide from.