I've worked on a fairly complex web app with advanced graphic effects. It used Angular, and I can confirm anything this article says, and more. For instance, it's extremely complex to get a CSS animation perform reasonably well on Android, compared to old iPhones.

I don't think V8 is a problem per se, it's the whole browser that underperforms on mobile. The only positive point is that at least it updates quickly. Sometimes minor versions of iOS introduces bugs that you don't ever know when they will be fixed.