Google doesn't have any issue having to deal with it for iOS.

I'm sure they have many issues with it, but they just don't have any options. Ditching Windows 10 S is an option since it has such a small market share.

I bet outside US it will have much more market share than Chromebooks.

M$ Edge on Android uses WebKit.

I feel like the 'M$' pejorative is a bit out dated and not really representative of Microsoft as a company anymore.

Apple, and Google practices as of late do seem sufficiently profit oriented to the point of poor consumer experience. Throw Facebook and Twitter in the mix for good measure. At the very least MS is no longer the only bully in the room....if they are still a bully at all.

I'm not sure I've seen quite as drastic a shift in fundamental thinking from a company as I've seen from Microsoft in recent years (under Nadella).

tl;dr - Any large and diversified (tech) company has so many powerful stakeholders within the company that decisions bubble up which are in the best interest of those stakeholders and their departments, not necessarily the consumer.

It was a cost-saving measure, the Edge engine doesn't run on anything that isn't Windows.

Firefox for Android uses it's own engine.

But it's not compulsory on android.