[jscholes]

> What if the two video files are of different durations? There’s a hornet’s nest of potential issues, but I’d take the occasional stings over the status quo any week of the day.

It's very easy to say things like this when you're not proposing a standards update that browser developers then have to implement. HTML is littered with examples of elements, attributes, whatever, that aren't consistently supported because browser developers disagree with, or just don't know, the details of how they're supposed to work. Case and point, focus management when invoking or moving within a modal created via the native dialog element.

In theory, this single user would be okay with the fact that switching video quality or size might do something weird if the underlying videos aren't compatible because of length. In practice, someone has to develop the code to make or let the "something weird" happen, define what it is, define what conditions trigger it, and so on.