You're reading it too politically. It says right up in the first paragraph:

> While LLVM is an excellent optimizer, it isn’t specifically designed for the optimization challenges of dynamic languages like JavaScript.

LLVM was, more-or-less, designed around C++ semantics. B3 is not going to be a better C++ compiler than LLVM. LLVM is not going to be a better JS compiler than B3. They're taking different evolutionary paths.