I have a potentially untestable theory that the reason why browser testing is so complex is because there is no browser that was built for testing. I almost always find that if my code is becoming difficult to test it's because I've made choices that are antagonistic to automation. The better my code is for unit testing, the easier the integration tests tend to be.
Selenium and friends are clearly hamstrung by browsers being antagonistic to E2E testing.
However it's safe to assume that this browser would have a significantly lighter footprint given that it's built "embedded first".
The only problem is that the engine is proprietary. I'm not sure about licensing when it is released. Regardless, I assume there would be nothing stopping people from bringing it onboard for tests/whatever else they dream up.