It's more of a branch than an actual fork. It's using an automated build process where they add/tweak/enable/disable stuff on top. The analogy I like to use is

It's more of a branch than an actual fork. It's using an automated build process where they add/tweak/enable/disable stuff on top. The analogy I like to use is they (Chromium-based browsers) are in another lane on the same road whereas a complete fork diverges to their own road. The former is still beholden to whatever direction the Chrome road goes.