I think I understand that, but it's still not clear to me how the type of the lock is the cause of the problem: the problem as far as I can see it is that the h

I think I understand that, but it's still not clear to me how the type of the lock is the cause of the problem: the problem as far as I can see it is that the hypothetical programmer isn't acquiring a lock (regardless of type) before starting their operation and then holding it until completion. Mandatory locking certainly has its issues/annoyances, but in terms of the situation I quoted, if used properly [1], it works fine and there is no risk of unexpected results due to races. [1] acquire lock for maximum level of operations you might need and hold it all the way through to completion, or to avoid holding a lock on the object for too long, get and release multiple locks verifying as needed that the data hasn't changed each time