And in at least one regard it's entirely true: on iOS, everything uses WebKit.
If anything, it was a fork of Konqueror.
Edit: It was widely speculated that Apple would use gecko for Safari and a shock when they announced they would use the relatively little known KHTML engine. The decision was based on KHTML having much cleaner code. I haven't looked at the Mozilla code in many years, but it was pretty gnarly back then. Lots of old cruft from the Netscape days. In comparison, KHTML was beautiful.
Edit: This post prompted me to Google for it: https://developer.mozilla.org/en-US/docs/Tools/Debugger/How_...
Move along, nothing to see.. :-\
Looking good, will give it another go.
Firefox is generally still a little buggier and less performance in my experience, but not so much that I want to switch back. Hopefully they can stay relevant.
But Chromes debugger and performance analysis still is a lot more capable.