A big part of the score is compilation time, which improves a lot with Liftoff, our baseline compiler for WebAssembly in V8. We've been in contact with the benchmark authors and have identified other bottlenecks in our engine (e.g. instantiation time), which we are now working on optimizing. Look forward to some increasing scores soon :)
Liftoff is still substantially slower at initial compilation than Firefox. Are there any plans to close the gap? A Unity exported game takes over 40 seconds for a new model low end Chromebook to compile. The upcoming 3 fold decrease will be nice, but FF could do it in 2 seconds on the same hardware.
We still have a bottleneck at instantation time where we compile many JS<->WASM wrappers. We are working on parallelizing this compilation as well, so we'll get another bump out of that.