It's long been my hypothesis that allowing passengers to check even one bag would help operational performance, purely anecdotal watching so many bags get gate-checked on U.S. carriers. To me, that appears to be critical path workflow with no slack - if they're tagging bags on the jetway when the door could be closed, it's lost time.

But I know nothing about the regular checked-bag workflow and how often it becomes critical path. Every once in a while, the captain will say something like "just a few more minutes while we load the last bags", but it's never specific whether those are originating bags, connecting bags, cargo, etc.

The test case in the U.S. would be Southwest Airlines. They used to have fantastic operations - I flew them in part because of how reliable they were. But in the past few years it's gotten vastly worse, and they have not changed their baggage policies. So that isn't the variable in this case...