1. Are those glissade "trails" down the side of the ledge from the top? (in Bob's picture) If so, please comment on the practice from this location.
Yes, they're glissade trails. In good conditions, glissading from the top is a nice way to descend and save some time.
I glissaded that route with a group on a June day, two days after a storm. We all had full backpacks, and one of the group did a 360 forward roll during the descent, but came out ok. We descended in the morning after camping on the summit, and the snow was soft.
However, in poor conditions, it can be deadly. If the snow has been through a number of freeze/thaw cycles, and people descend late in the afternoon, the upper part is still in the sun and conditions might seem ok. But the mountain shadow starts from the bottom and moves upslope as the sun moves across the sky, so the bottom can freeze up first. People have died glissading that section in icy conditions.
2. Changing the trail to accommodate melting patterns -- was such a luxury a sign of the times or would such an undertaking be considered today?
Trails seem to get changed or improved, and this trail is one of the most traveled in the Sierra, so fixing it makes sense. I am sure with budgets these days, there is not as much trail construction as in the past.
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As for searching, I don't think your question regarding moving the trail has been discussed before. But Bob R posted another excellent composite picture of the switchbacks maybe two years ago, but I sure can't find it now. It was one where you could zoom in and count all the hikers on the switchbacks.
