[timothya]

While you're right that it's up to the browser to fix, that can be a very time consuming process (especially for something as tricky as video). YouTube doesn't want to wait around for browser vendors to fix things, so they work around it themselves (just like happened in the opposite direction for this bug).

Finding workarounds for browser bugs is a common theme for the work that web developers do. Yes, browser vendors should fix the bugs, but in the meantime, there's no reason to have a bad user experience.