I use Firefox on my non-work machines ... in an ideal world, enough people would do that to prevent the "best in Internet Explorer" web of the dark ages, but I'll take getting forced to use Webkit on my phone over that, even if I'd prefer a "true" Firefox.
Is Webkit really so far diverged from Blink that the rendering result is different? I realize that Webkit doesn't support a bunch of stuff that Google pushed into Blink (like Web bluetooth, for instance), but I thought the end result wasn't that different.
Worse yet, many people have older iPhones with outdated Safari. You can't tell them to just install another browser, because under the hood Apple mandates that all other browsers are still the same outdated Safari engine.
If you want to track these issues down, you need to invest in an Apple based set up. You can't run Safari outside of the Apple ecosystem to track these issues down. It is bad enough that people are now offering pay as you go Safari instances for testing. Apple gatekeeps, Apple invents problems and developers are stuck with the bag.
So no, it is not in anyway good for the browser landscape or the web, it only serves the interest of one company: Apple.