I have gone over this again and again and really can't figure out how someone goes "down" the trail. I know the trail is going down after Trail Crest, but picking the down trail over the up trail seems a bit odd. At this part of the trail, in clear weather you can see the hut can't you??? And that is up. I am sure if it's snowing, icy or bad weather, you could go down, but wouldn't you notice after 10 to 15 minutes that you've really been going down for a long, long time?
part of the confusion in your question relates to a misunderstanding, I think. It is NOT the hiker descending from Trail Crest to the intersection that chooses the wrong trail. It is the hiker descending from WHITNEY, that chooses the wrong trail.
The issue, I think explained some time ago by Bob, is that a person has spent a day or two climbing up, up, up, up, up, except for a very short segment that drops from Trail Crest to the intersection, and then they go up, up, up, up.
By the time that a person heads back down, they now have in their heads: down, down, down, down. They have forgotten the small segment of change. They know down. They come to the intersection, and the reptilian part of their brain that is probably most active at this point, when confronted with the question "up or down?", responds down, down, down.
Add into the equation that most people have a degree of exhaustion, and a degree of dehydration, and a degree of hypoxia.....and you understand that their brain is not working correctly, clearly, optimally. And they want to get DOWN.
It takes a pretty assertive cue at this point to break through the fog and haze of blanked out thinking, to get them to UP. (Isn't that part of the hike already over??)
There is no doubt that people should not have this difficulty. They do.
There is no doubt that SAR resources should not be wasted on this. They are.
There is a sign there: it doesn't work some of the time.
The sign is easily subject to misinterpretation: happens commonly.
I agree that a VERY simple fix, is to improve the existing sign. Doesn't require a NEPA finding, Doesn't require space science. Probably takes less than an hour. No additional evil signs.