It is a fork, but that was really long time ago, most parts of both engines were completely rewritten so for all intents and purposes these are completely different engines.
They’ve splintered a ton over the years for sure, but there are still similarities. But yes, this isn’t like the first few years when Blink was just WebKit with V8.
But on the whole, Blink is still more similar to WebKit than it is to Gecko.
But on the whole, Blink is still more similar to WebKit than it is to Gecko.