This should be a rule though
If nothing else, a top rider making such a mistake indicates the importance of walking a course properly. I’m always surprised at how many riders “walk a course” while enjoying a good gossip in company with their friends, on their phone running their business, who give whole sections of the course a glance from a far distance, who really don’t notice the terrain and many don’t even look for the alternative jump when one exists. It’s lovely to have confidence that your horse will take all the straight routes but reality sometimes bites.
Boyd did the black flag option. Crossing your tracks is no longer an issue. If you have a combination that is A,B,C but there is a black flag option for B or C it is recognized that if there is a stop in the straight route you go directly to the black flag even if you cross your tracks. You are presenting to a new jump and it is no longer an issue.