I guess so, if it's not exactly "one out, one in", that would constantly reorder packets. I think head-drop, like the article says is really the best trivial solution the more I think about it.
Yep, but IP doesn't provide an ordering guarantee at the link level anyway, and higher-level protocols have sequence numbers so they can reassemble things correctly. If those higher-level mechanisms aren't up for the task of handling lots of small reorderings, that would obviously be an issue.