Puntosaurus, I reckon downwind quickstops are relevant and should be taught, with the following points kept in mind:
1. Many helicopter pilots go on to do jobs that require low flying (mustering, ag, filming etc) where this kind of manoueuvering is required, and learning the basics early is to my mind better than getting them as an 'add-on' later.
2. During the sequences, when you're flying downwind you have airspeed on your side. Once the speed reduction is commenced, you're flaring and turning into wind. The collective is partially lowered, so you're not in the high power part of the avoid curve as you would be on takeoff at the same height AGL, plus you have a lot of flare effect on your side.
3. Quickstops are a great judgement/skills exercise, a chance for students to get to know their aircraft's capabilities (and their own) without being silly about it. They fall into the worthwhile calculated risk category, as I see it.