We have seen how WebOS and FirefoxOS turned out. Wishing Google good luck with PWAs on slow devices. Having seen Inbox web app animations and memory usage I'm not holding my breath
But you do have to admit that UI latency on it was quite high compared to iOS. I mean, so was Android back then, but they improved it significantly.
There’s good reason to blelieve that given enough time and even a fraction of resources that the Android team had WebOS would be able to significantly up their performance game (I say a fraction of resources because there is a lot of well funded open source development being done to improve web tech on mobile, through Chromium, WebKit and Firefox that would be leveraged).